How to find the solution to an inequality with addition - PSAT Math

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Question

What values of x make the following statement true?

|x – 3| < 9

Answer

Solve the inequality by adding 3 to both sides to get x < 12. Since it is absolute value, x – 3 > –9 must also be solved by adding 3 to both sides so: x > –6 so combined.

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Question

Solve for .

Answer

Absolute value problems always have two sides: one positive and one negative.

First, take the problem as is and drop the absolute value signs for the positive side: z – 3 ≥ 5. When the original inequality is multiplied by –1 we get z – 3 ≤ –5.

Solve each inequality separately to get z ≤ –2 or z ≥ 8 (the inequality sign flips when multiplying or dividing by a negative number).

We can verify the solution by substituting in 0 for z to see if we get a true or false statement. Since –3 ≥ 5 is always false we know we want the two outside inequalities, rather than their intersection.

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Question

If –1 < w < 1, all of the following must also be greater than –1 and less than 1 EXCEPT for which choice?

Answer

3_w_/2 will become greater than 1 as soon as w is greater than two thirds. It will likewise become less than –1 as soon as w is less than negative two thirds. All the other options always return values between –1 and 1.

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Question

If x+1< 4 and y-2<-1 , then which of the following could be the value of ?

Answer

To solve this problem, add the two equations together:

x+1<4

y-2<-1

x+1+y-2<4-1

x+y-1<3

x+y<4

The only answer choice that satisfies this equation is 0, because 0 is less than 4.

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Question

If , which of the following could be a value of ?

Answer

In order to solve this inequality, you must isolate on one side of the equation.

Therefore, the only option that solves the inequality is .

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Question

What values of make the statement true?

Answer

First, solve the inequality :

Since we are dealing with absolute value, must also be true; therefore:

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