Question

What are the factors of x2 - 81?

(x + 9)(x - 9)
(x - 9)(x - 9)
(x + 3)(x - 27)
Prime

Answer 1

difference of square s \[\huge\rm a^2 - b^2 = (a+b)(a-b)\]

Answer 2

Diffrence of squares
\[\huge~\rm~\sqrt{ x^2}=\sqrt{81}\]

Answer 3

take square root of both term
write your answer in two parenthses
(sqrt of first term + sqrt of 2nd term )( sqrt of first term - sqt of 2nd term )

Answer 4

You can use foil here & just work backwards aswell, so looking at answer choice #1,
(x+9)(x-9)

"F" first: X * X = X^2
"O" outside: X * 9 = 9x
"I" inside: -9 * X = -9x
"L" last: 9 * (-9) = -81

So you have:
x^2 + 9x - 9x -81

Now simplify:
x^2 -81

Thats how i solved my equations in school. hope it helps :)

Answer 5

help plz @Mehek14

Answer 6

what do you think is the answer?

Answer 7

B?

Answer 8

no
-9 * -9 = +81 not -81

Answer 9

it would be (x + 9)(x - 9)

Answer 10

because x*x = \(x^2\)
\(9x+-9x=0\\9*-9=-81\\x^2+0-81\\x^2-81\)

Answer 11

oh ok i think i get it now