How to factor a variable - SAT Math
Card 0 of 10
Factor the following variable
(x2 + 18x + 72)
Factor the following variable
(x2 + 18x + 72)
You need to find two numbers that multiply to give 72 and add up to give 18
easiest way: write the multiples of 72:
1, 72
2, 36
3, 24
4, 18
6, 12: these add up to 18
(x + 6)(x + 12)
You need to find two numbers that multiply to give 72 and add up to give 18
easiest way: write the multiples of 72:
1, 72
2, 36
3, 24
4, 18
6, 12: these add up to 18
(x + 6)(x + 12)
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When 
is factored, it can be written in the form 
, where 
, 
, 
, 
, 
, and 
are all integer constants, and 
.
What is the value of 
?
When
What is the value of
Let's try to factor x2 – y2 – z2 + 2yz.
Notice that the last three terms are very close to y2 + z2 – 2yz, which, if we rearranged them, would become y2 – 2yz+ z2. We could factor y2 – 2yz+ z2 as (y – z)2, using the general rule that p2 – 2pq + q2 = (p – q)2 .
So we want to rearrange the last three terms. Let's group them together first.
x2 + (–y2 – z2 + 2yz)
If we were to factor out a –1 from the last three terms, we would have the following:
x2 – (y2 + z2 – 2yz)
Now we can replace y2 + z2 – 2yz with (y – z)2.
x2 – (y – z)2
This expression is actually a differences of squares. In general, we can factor p2 – q2 as (p – q)(p + q). In this case, we can substitute x for p and (y – z) for q.
x2 – (y – z)2 = (x – (y – z))(x + (y – z))
Now, let's distribute the negative one in the trinomial x – (y – z)
(x – (y – z))(x + (y – z))
(x – y + z)(x + y – z)
The problem said that factoring x2 – y2 – z2 + 2yz would result in two polynomials in the form (ax + by + cz)(dx + ey + fz), where a, b, c, d, e, and f were all integers, and a > 0.
(x – y + z)(x + y – z) fits this form. This means that a = 1, b = –1, c = 1, d = 1, e = 1, and f = –1. The sum of all of these is 2.
The answer is 2.
Let's try to factor x2 – y2 – z2 + 2yz.
Notice that the last three terms are very close to y2 + z2 – 2yz, which, if we rearranged them, would become y2 – 2yz+ z2. We could factor y2 – 2yz+ z2 as (y – z)2, using the general rule that p2 – 2pq + q2 = (p – q)2 .
So we want to rearrange the last three terms. Let's group them together first.
x2 + (–y2 – z2 + 2yz)
If we were to factor out a –1 from the last three terms, we would have the following:
x2 – (y2 + z2 – 2yz)
Now we can replace y2 + z2 – 2yz with (y – z)2.
x2 – (y – z)2
This expression is actually a differences of squares. In general, we can factor p2 – q2 as (p – q)(p + q). In this case, we can substitute x for p and (y – z) for q.
x2 – (y – z)2 = (x – (y – z))(x + (y – z))
Now, let's distribute the negative one in the trinomial x – (y – z)
(x – (y – z))(x + (y – z))
(x – y + z)(x + y – z)
The problem said that factoring x2 – y2 – z2 + 2yz would result in two polynomials in the form (ax + by + cz)(dx + ey + fz), where a, b, c, d, e, and f were all integers, and a > 0.
(x – y + z)(x + y – z) fits this form. This means that a = 1, b = –1, c = 1, d = 1, e = 1, and f = –1. The sum of all of these is 2.
The answer is 2.
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Factor 9_x_2 + 12_x_ + 4.
Factor 9_x_2 + 12_x_ + 4.
Nothing common cancels at the beginning. To factor this, we need to find two numbers that multiply to 9 * 4 = 36 and sum to 12. 6 and 6 work.
So 9_x_2 + 12_x_ + 4 = 9_x_2 + 6_x_ + 6_x_ + 4
Let's look at the first two terms and last two terms separately to begin with. 9_x_2 + 6_x_ can be simplified to 3_x_(3_x_ + 2) and 6_x_ + 4 can be simplified into 2(3_x_ + 2). Putting these together gets us
9_x_2 + 12_x_ + 4
= 9_x_2 + 6_x_ + 6_x_ + 4
= 3_x_(3_x_ + 2) + 2(3_x_ + 2)
= (3_x_ + 2)(3_x_ + 2)
This is as far as we can factor.
Nothing common cancels at the beginning. To factor this, we need to find two numbers that multiply to 9 * 4 = 36 and sum to 12. 6 and 6 work.
So 9_x_2 + 12_x_ + 4 = 9_x_2 + 6_x_ + 6_x_ + 4
Let's look at the first two terms and last two terms separately to begin with. 9_x_2 + 6_x_ can be simplified to 3_x_(3_x_ + 2) and 6_x_ + 4 can be simplified into 2(3_x_ + 2). Putting these together gets us
9_x_2 + 12_x_ + 4
= 9_x_2 + 6_x_ + 6_x_ + 4
= 3_x_(3_x_ + 2) + 2(3_x_ + 2)
= (3_x_ + 2)(3_x_ + 2)
This is as far as we can factor.
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Factor and simplify:
Factor and simplify:
is a difference of squares.
The difference of squares formula is 
.
Therefore, 
= 
.
The difference of squares formula is
Therefore,
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If 
, and 
, what is the value of 
?
If
The numerator on the left can be factored so the expression becomes 
, which can be simplified to 
Then you can solve for 
by adding 3 to both sides of the equation, so 
The numerator on the left can be factored so the expression becomes
Then you can solve for
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Factor:
Factor:
We can first factor out 
:
This factors further because there is a difference of squares:
We can first factor out
This factors further because there is a difference of squares:
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Solve for x:
Solve for x:
First, factor.
Set each factor equal to 0
Therefore,
First, factor.
Set each factor equal to 0
Therefore,
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A semi truck unloaded weighs 
. When the trailer compartment is loaded to half capacity with soda, the semi weighs 
. What will the truck weigh when the compartment is loaded to 
capacity with the same kind of soda?
A semi truck unloaded weighs
This word problem can be broken down into a basic algebraic equation:
A half-loaded semi weighs 37,000 lbs. Subtracting the weight of the truck, we can determine that a half load weighs 17,000 lbs:
From that, we can determine that a full load = 34,000 lbs:
Knowing the weight of a full load, we can calculate the weight of a 3/4 load:
Add the weight of the truck to get the total weight:
This word problem can be broken down into a basic algebraic equation:
A half-loaded semi weighs 37,000 lbs. Subtracting the weight of the truck, we can determine that a half load weighs 17,000 lbs:
From that, we can determine that a full load = 34,000 lbs:
Knowing the weight of a full load, we can calculate the weight of a 3/4 load:
Add the weight of the truck to get the total weight:
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A group of scientists form a global collective of temperature and climate data. U.S. temperature measurements are in Fahrenheit and must be converted to Celsius. If the average spring temperature for New York was 
Fahrenheit, what is the temperature value in Celsius?
The Fahrenheit to Celsius conversion equation is as follows:
A group of scientists form a global collective of temperature and climate data. U.S. temperature measurements are in Fahrenheit and must be converted to Celsius. If the average spring temperature for New York was
The Fahrenheit to Celsius conversion equation is as follows:
You can solve this problem by substituting in 
for 
and solving for 
:
That means that 
Fahrenheit is the same as 
Celsius.
You can solve this problem by substituting in
That means that
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Factor to the simplest form: 
Factor to the simplest form:
Group all the terms with the 
variable.
Pull out an 
term from parentheses.
There are no more common factors.
The correct answer is: 
Group all the terms with the
Pull out an
There are no more common factors.
The correct answer is:
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