Graphing - GMAT Quantitative Reasoning

Card 0 of 20

Question

Find the graph of the linear function .

I) passes through the points and .

II) intercepts the -axis at .

Answer

Find the graph of the linear function .

I) passes through the points and .

II) intercepts the -axis at .

Using I), we can find the slope of the function, and then we can start at either point and extend the slope in either direction to find our graph:

So, using I) we are able to find the slope, from which we can find our graph

II) gives us one point, but without any more information, we cannot use II) by itself to find the rest of the graph

So:

Statement I is sufficient to answer the question, but statement II is not sufficient to answer the question.

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Question

Find the graph of .

I) is a linear equation which passes through the point .

II) crosses the y-axis at 1300.

Answer

Find the graph of .

I) is a linear equation which passes through the point .

II) crosses the y-axis at 1300.

To graph a linear equation, we need some combination of slope, y-intercept, or two points.

Statement I tells us is linear and gives us one point.

Statement II gives us the y-intercept of .

We can use Statement I and Statement II to find the slope of . Then, we can plot the given points and continue the line in either direction to get our graph.

Slope:

Plugging in the provided value of , 1300, we have the equation of the line :

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Question

Graph a line, if possible.

Statement 1: The slope is 4.

Statement 2: The y-intercept is 4.

Answer

Statement 1): The slope is 4.

Write the slope-intercept form, and substitute the slope.

The point and the y-intercept are unknown. Either of these will be needed to solve for the graph of this line.

Statement 1) by itself is not sufficient to graph a line.

Statement 2): The y-intercept is 4.

Substitute the y-intercept into the incomplete formula.

The function can then be graphed on the x-y coordinate plane.

Therefore:

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Question

Define a function as follows:

for nonzero real numbers .

Give the equation of the vertical asymptote of the graph of .

Statement 1:

Statement 2:

Answer

Only positive numbers have logarithms, so:

Therefore, the vertical asymptote must be the vertical line of the equation

.

Statement 1 alone gives that . is the reciprocal of this, or , and , so the vertical asymptote is .

Statement 2 alone gives no clue about either , , or their relationship.

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Question

Define a function as follows:

for nonzero real numbers .

Give the equation of the vertical asymptote of the graph of .

Statement 1:

Statement 2:

Answer

Since a logarithm of a nonpositive number cannot be taken,

Therefore, the vertical asymptote must be the vertical line of the equation

.

Each of Statement 1 and Statement 2 gives us only one of and . However, the two together tell us that

making the vertical asymptote

.

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Question

Define a function as follows:

for nonzero real numbers .

Does the graph of have a -intercept?

Statement 1: .

Statement 2: .

Answer

The -intercept of the graph of the function , if there is one, occurs at the point with -coordinate 0. Therefore, we find :

This expression is defined if and only if is a positive value. Statement 1 gives as positive, so it follows that the graph indeed has a -intercept. Statement 2, which only gives , is irrelevant.

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Question

Define a function as follows:

for nonzero real numbers .

Does the graph of have a -intercept?

Statement 1: .

Statement 2: and have different signs.

Answer

The -intercept of the graph of the function , if there is one, occurs at the point with -coordinate 0. Therefore, we find :

This expression is defined if and only if is a positive value. However, the two statements together do not give this information; the values of and from Statement 1 are irrelevant, and Statement 2 does not reveal which of and is positive and which is negative.

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Question

Define a function as follows:

for nonzero real numbers .

Where is the vertical asymptote of the graph of in relation to the -axis - is it to the left of it, to the right of it, or on it?

Statement 1: and are both positive.

Statement 2: and are of opposite sign.

Answer

Since only positive numbers have logarithms,

Therefore, the vertical asymptote must be the vertical line of the equation

.

Statement 1 gives irrelevant information. But Statement 2 alone gives sufficient information; since and are of opposite sign, their quotient is negative, and is positive. This locates the vertical asymptote on the right side of the -axis.

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Question

Define a function as follows:

for nonzero real numbers .

Where is the vertical asymptote of the graph of in relation to the -axis - is it to the left of it, to the right of it, or on it?

Statement 1: and are both positive.

Statement 2: and are of opposite sign.

Answer

Since only positive numbers have logarithms, the expression must be positive, so

Therefore, the vertical asymptote must be the vertical line of the equation

.

In order to determine which side of the -axis the vertical asymptote falls, it is necessary to find the sign of ; if it is negative, it is on the left side, if it is positive, it is on the right side.

Assume both statements are true. By Statement 1, is positive. If is positive, then is negative, and vice versa. However, Statement 2, which mentions , does not give its actual sign - just the fact that its sign is the opposite of that of , which we are not given either. The two statements therefore give insufficient information.

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Question

Define a function as follows:

for nonzero real numbers .

Give the equation of the vertical asymptote of the graph of .

Statement 1:

Statement 2:

Answer

Since only positive numbers have logarithms,

Therefore, the vertical asymptote must be the vertical line of the equation

.

Assume both statements to be true. We need two numbers and whose sum is 7 and whose product is 12; by trial and error, we can find these numbers to be 3 and 4. However, without further information, we have no way of determining which of and is 3 and which is 4, so the asymptote can be either or .

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Question

Define a function as follows:

for nonzero real numbers .

What is the equation of the vertical asymptote of the graph of ?

Statement 1: and are of opposite sign.

Statement 2:

Answer

Since only positive numbers have logarithms,

Therefore, the vertical asymptote must be the vertical line of the equation

.

In order to determine which side of the -axis the vertical asymptote falls, it is necessary to find the sign of ; if it is negative, it is on the left side, and if it is positive, it is on the right side.

Statement 1 alone only gives us that is a different sign from ; without any information about the sign of , we cannot answer the question.

Statement 2 alone gives us that , and, consequently, . This means that and are of opposite sign. But again, with no information about the sign of , we cannot answer the question.

Assume both statements to be true. Since, from the two statements, both and are of the opposite sign from , and are of the same sign. Their quotient is positive, and is negative, so the vertical asymptote is to the left of the -axis.

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Question

Define a function as follows:

for nonzero real numbers .

Where is the vertical asymptote of the graph of in relation to the -axis - is it to the left of it, to the right of it, or on it?

Statement 1:

Statement 2:

Answer

Only positive numbers have logarithms, so:

Therefore, the vertical asymptote must be the vertical line of the equation

.

In order to determine which side of the -axis the vertical asymptote falls, it is necessary to find out whether the signs of and are the same or different. If and are of the same sign, then their quotient is positive, and is negative, putting on the left side of the -axis. If and are of different sign, then their quotient is negative, and is positive, putting on the right side of the -axis.

Statement 1 alone does not give us enough information to determine whether and have different signs. , for example, but , also.

From Statement 2, since the product of and is negative, they must be of different sign. Therefore, is positive, and falls to the right of the -axis.

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Question

In which quadrant is the point located: I, II, III, or IV?

Statement 1:

Statement 2:

Answer

Assume Statement 1 alone. The set of points that satisfy the equation is the set of all points on the line of the equation

which will pass through at least two quadrants on the coordinate plane. Therefore, Statement 1 provides insufficient information.

Now assume Statement 2 alone. The set of points that satisfy the equation is the set of all points of the circle of the equation

This circle has as its center and as its radius. Since its center is , which is 5 units away from its closest axis, and the radius is less than 5 units, the circle never intersects an axis, so it is contained entirely within the same quadrant as its center. The center has negative - and -coordinates, placing it, and the entire circle, in Quadrant III.

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Question

In which quadrant is the point located: I, II, III, or IV?

Statement 1:

Statement 2:

Answer

Assume Statement 1 alone. The set of points that satisfy the equation is the set of all points on the line of the equation

,

which will pass through at least two quadrants on the coordinate plane. Therefore, Statement 1 provides insufficient information. By the same argument, Statement 2 is also insuffcient.

Now assume both statements to be true. The two statements together form a system of linear equations which can be solved using the elimination method:

Now, substitute back:

The point is , which has a positive -coordinate and a negative -coordinate and is consequently in Quadrant IV.

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Question

In which quadrant is the point located: I, II, III, or IV?

Statement 1:

Statement 2:

Answer

Assume Statement 1 alone. The points and each satisfy the condition of the statement; however, the former is in Quadrant I, having a positive -coordinate and a positive -coordinate; the latter is in Quadrant IV, having a positive -coordinate and a negative -coordinate.

Assume Statement 2 alone. The points and each satisfy the condition of the statement, since . However, the former is in Quadrant IV, having a positive -coordinate and a negative -coordinate; the latter is in Quadrant II, having a negative -coordinate and a positive -coordinate.

Assume both statements to be true. Statement 2 can be rewritten as ; since is positive from Statement 1, is negative. Since the point has a positive -coordinate and a negative -coordinate, it is in Quadrant IV.

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Question

True or false: and are in the same quadrant of the rectangular coordinate plane.

Statement 1: and are of different sign.

Statement 2: and are of the same sign.

Answer

Two points in the same quadrant have -coordinates of the same sign and -coordinates of the same sign.

It is possible for two points fitting the condition of Statement 1 to be in the same quadrant; and are two such points. However, it is also possible for two such points to be in different quadrants; and are two such points. Therefore, Statement 1 alone gives insufficient information. By the same argument, Statement 2 alone gives insufficient information.

Assume both statements are true. and are of different sign by Statement 1. By Statement 2, and are of the same sign; therefore, they are both of the same sign as and the sign opposite that of , or vice versa. Therefore, in one ordered pair, both numbers are positive or both are negative, and in the other ordered pair, one number is positive and the other is negative. The two ordered pairs cannot represent points in the same quadrant.

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Question

True or false: , , and are collinear points.

Statement 1: and

Statement 2:

Answer

Assume Statement 1 alone. The equations can be rewritten as follows:

The - and -coordinates of are the arithmetic means of those of and , so is the midpoint of the segment with those endpoints. Therefore, the three points are collinear.

Assume Statement 2 alone. The statement can be rewritten as follows:

The first expression is the slope of the line through and ; the second expression is the slope of the line through and . Since the slopes are equal, the three points are collinear.

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Question

True or false: and are in the same quadrant of the rectangular coordinate plane.

Statement 1: and are of different sign.

Statement 2: and are of different sign.

Answer

Two points in the same quadrant have -coordinates of the same sign and -coordinates of the same sign; however, from Statement 1 alone, we find that the -coordinates of the points have different signs, and from Statement 2 alone, we find that this holds for the -coordinates. Therefore, from either statement alone, the points can be proved to be in different quadrants.

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Question

In which quadrant is the point located: I, II, III, or IV?

Statement 1:

Statement 2:

Answer

Assume both statements. The points and each satisfy the conditions of both statements, since , , and . The former is in Quadrant I, having a positive -coordinate and a positive -coordinate; the latter is in Quadrant IV, having a positive -coordinate and a negative -coordinate.

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Question

True or false: , , and are collinear points.

Statement 1:

Statement 2: and

Answer

Assume Statement 1 alone.

The proportion statement

can be rewritten by setting the reciprocals of the expressions equal:

The first expression is the slope of the line through and ; the second is the slope of the line through and . Since the slopes are equal, the three points are on the same line - collinear.

The three points cannot be assumed to be collinear from Statement 2 alone. For example, , , and collectively fit the condition of Statement 2, and all three points are easily seen to be on the line of the equation . However, , , and collectively fit the condition of Statement 2, and while the line through the first two points is again , is off that line, so the three points are noncollinear.

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