Question

Which factors can be multiplied together to make the trinomial 5x2 + 8x – 4? Check all that apply.

(x + 1)
(2x + 1)
(x + 2)
(5x + 1)
(5x – 2)

Answer 1

x+2 and 5x-2

Explanation:

Answer 2

x+2

5x-2

Explanation:

There is only 2 binomials that will multiply together that will give the given trinomial.

ax^2+bx+c

5x^2+8x-4

Goal: Find two numbers that multiply to be a*c and add up to be b.

We will use this goal to factor our trinomial.

a=5

b=8

c=-4

--------

a*c=-20

b=8

Can you think of two numbers that multiply to be -20 and add up to be 8? I hope you said 10 and -2.

So we are going to replace 8x with -2x+10x.

5x^2+8x-4

5x^2-2x+10x-4

We are going to pair the first terms together and the second two terms together like so:

(5x^2-2x)+(10x-4)

Now we are going to factor each pair.

x(5x-2)+2(5x-2)

(5x-2)(x+2)

So (x+2) is a factor of the given trinomial and (5x-2) is a factor of the given trinomial.