Question

Select the correct answer.

What are the zeros of this quadratic function?

f(x) = (x − 7)(x + 8)

A.
x = 7 and x = -8
B.
x = -7 and x = 8
C.
x = 0 and x = -8
D.
x = 0 and x = 7

Answer 1

The answer would be A

Explanation:

You can find the answer by doing the FOIL method.

Answer 2

You use the FOIL method, and how you do this is -

(x - 7) (x + 8)

Multiply the first x by both numbers in the second factor. Which means, you multiply x by x and 8, the two in (x + 8).

With this, you get -
x^2 + 8x

Then do the same thing with -7.

-7x - 56

Then combine the two.
x^2 + 8x - 7x - 56

Combine like terms.

x^2 + x - 56

So now, 7 x 8 is 56
And -7 + 8 would be 1. And that is the value of “x” which is b in the form a^2x + bx + c.

Now with this, you take those two numbers and make the factors =
(x + 8) (x - 7)

Then you set these equal to 0.

x + 8 = 0

Subtract the 8 from both sides.

x = -8

————

x - 7 = 0

Add the 7 on both sides.

x = 7

Answer: A