All SAT Math Resources
Example Questions
Example Question #1 :How To Factor An Equation
Factor the following equation.
x2– 16
(x – 4)(x – 4)
(x + 4)(x + 4)
(x)(x – 4)
(x + 4)(x – 4)
(x2)(4 – 2)
(x + 4)(x – 4)
The correct answer is (x + 4)(x – 4)
We neen to factor x2– 16 to solve. We know that each parenthesis will contain an x to make the x2. We know that the root of 16 is 4 and since it is negative and no value of x is present we can tell that one 4 must be positive and the other negative. If we work it from the multiple choice answers we will see that when multiplying it out we get x2+ 4x – 4x – 16. 4x – 4x cancels out and we are left with our answer.
Example Question #1 :Equations / Solution Sets
If x3– y3= 30, and x2+ xy + y2= 6, then what is x2– 2xy + y2?
25
180
cannot be determined
5
24
25
First, let's factor x3– y3using the formula for difference of cubes.
x3– y3= (x – y)(x2+ xy + y2)
We are told that x2+ xy + y2= 6. Thus, we can substitute 6 into the above equation and solve for x – y.
(x - y)(6) = 30.
Divide both sides by 6.
x – y = 5.
The original questions asks us to find x2– 2xy + y2. Notice that if we factor x2– 2xy + y2using the formula for perfect squares, we obtain the following:
x2– 2xy + y2= (x – y)2.
Since we know that (x – y) = 5, (x – y)2must equal 52, or 25.
Thus, x2– 2xy + y2= 25.
The answer is 25.
Example Question #2 :How To Factor An Equation
if x – y = 4 and x2– y = 34, what is x?
9
12
15
10
6
6
This can be solved by substitution and factoring.
x2– y = 34 can be written as y = x2– 34 and substituted into the other equation: x – y = 4 which leads to x – x2+ 34 = 4 which can be written as x2– x – 30 = 0.
x2– x – 30 = 0 can be factored to (x – 6)(x + 5) = 0 so x = 6 and –5 and because only 6 is a possible answer, it is the correct choice.
Example Question #1 :How To Factor An Equation
Ifx2+ 2ax+ 81 = 0. Whena= 9, what is the value ofx?
9
0
3
–9
–18
–9
Whena= 9, thenx2+ 2ax+ 81 = 0 becomes
x2+ 18x+ 81 = 0.
This equation can be factored as (x+ 9)2= 0.
Therefore whena= 9,x= –9.
Example Question #5 :Factoring Equations
Iff(x) has roots atx= –1, 0 and 2, which of the following could be the equation forf(x)?
f(x) = x4+ x3– 2x2
f(x) = x2– x – 2
f(x) = x3– x2+ 2x
f(x) = x3– x2– 2x
f(x) = x2+ x – 2
f(x) = x3– x2– 2x
In general, if a function has a root atx=r, then (x –r) must be a factor off(x). In this problem, we are told thatf(x) has roots at –1, 0 and 2. This means that the following are all factors off(x):
(x –(–1)) =x+ 1
(x– 0) =x
and (x– 2).
This means that we must look for an equation forf(x) that has the factors (x+ 1),x, and (x –2).
We can immediately eliminate the functionf(x) =x2+x– 2, because we cannot factor anxout of this polynomial. For the same reason, we can eliminatef(x) =x2–x– 2.
Let's look at the functionf(x) =x3–x2+ 2x. When we factor this, we are left withx(x2–x+ 2). We cannot factor this polynomial any further. Thus,x+ 1 andx– 2 are not factors of this function, so it can't be the answer.
Next, let's examinef(x) =x4+x3– 2x2.
We can factor outx2.
x2(x2+x– 2)
When we factorx2+x– 2, we will get (x+ 2)(x –1). These factors are not the same asx– 2 andx+ 1.
The only function with the right factors isf(x) =x3–x2– 2x.
When we factor out anx, we get (x2–x– 2), which then factors into (x– 2)(x+ 1). Thus, this function has all of the factors we need.
The answer isf(x) =x3–x2– 2x.
Example Question #3 :How To Factor An Equation
Factor 36x2– 49y2.
(6x+ 7y)(6x+ 7y)
cannot be factored
6x2– 7y2
(6x+ 7y)(6x– 7y)
(6x– 7y)(6x– 7y)
(6x+ 7y)(6x– 7y)
This is a difference of squares. The difference of squares formula isa2–b2= (a+b)(a–b). In this problem,a= 6xandb= 7y.
So 36x2– 49y2= (6x+ 7y)(6x– 7y).
Example Question #202 :Algebra
Solve forx:
Find two numbers that add toand multiply to
Factors of
You can use
Then make each factor equal 0.
and
and
Example Question #203 :Algebra
Find the roots of
Factoring yieldsgiving roots ofand.
Example Question #204 :Algebra
Find the root of the equation above.
The numerator can be factored into.
Therefore, it can cancel with the denominator. Soimples.
Example Question #4 :Factoring Equations
Solve for.
Find all factors of 24
1, 2, 3,4, 6, 8, 12, 24
Now find two factors that add up toand multiply to;andare the two factors.
By factoring, you can set the equation to be
If you FOIL it out, it gives you.
Set each part of the equation equal to 0, and solve for.
and
and
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