How do you do this problem ?

Question

Find the product.
(x + 9)(x - 9)

x2 - 81
x2 - 18x - 81
x2 - 18
x2 + 18x - 81

Answer 1

(x + 9) (x - 9)
distribute

x^2 - 9x + 9x - 81

x^2 - 81

the first choice

Answer 2

FOIL (first, outside, inside, last)
x^2 + 9x - 9x -81 = 0
x^2 - 81 = 0
x^2 = 81
x = 9

Answer 3

to answer it you must use F.O.I.L. (first. outside, inside, last)

multiply x by x, then x by - 9, then x by 9, and finally -9 by 9.

you get x^2 -9x +9x -81 which reduces to x^2-81.

Answer 4

Remember the acronym FOIL.....
Multiply....
First...Outer...
Inner...Last.....

F = x2 (x*x)
O = -9x (-9*x)
I = +9x (9*x)
L = -81 (9*-9)

So.....x2-9x+9x-81 = x2-81

Answer 5

FOIL.

F = multiply the 2 first terms

O = multiply the 2 outer terms

I = multiply the two inner terms

L = multiply the last 2 terms

So you get:

F = x^2

O = -9x

I = 9x

L = -81

Answer x^2 - 81

Answer 6

to do this question you foil (first, outer, inner, last)

so you do x *x, then x*-9 then go to the inner and get +9 * x and +9*-9

so you get

x^2 +9x - 9x -81 which goes to

x^2 -81
so the first one is your answer!

Answer 7

(x + 9)(x - 9)
(x)(x - 9) + (9)(x - 9)
(x2 - 9x) + (9x - 81)
x2 - 9x + 9x - 81
x2 - 81

There. Hope that helps

Answer 8

(x+9)(x-9)= 0
x2-9x+9x-81= 0
x2-81= 0
x2= 81
Therefore; x = (+ or -) 9 .
==> +9 and -9 .

Answer 9

FOIL. first multiply the first number (or variable) of each set of parenthesis, then do the same thing with outside numbers, the inside numbers and the last. then add them up.