could someone show me what i did wrong?

Question

Factor the following.

81−4^r2

 

that's what i got (9-2^r) (9+2^r)

but its wrong. what do i do?

Answer 1

I believe your polynomial supposed to be:

81-4r²

 

This is the difference of two squares.

81 = 9²

4r² = (2r)²

 

81 - 4r² = 9² - (2r)²

 

The formula for difference of two squares is

a²-b² = (a-b)(a+b)

For this equation a=9, b=2r

 

81-4r² = (9-2r)(9+2r)

Answer 2

81−4^r2

that's what i got (9-2^r) (9+2^r)
but its wrong. what do i do?

 

=========================

 

Actually, your result corresponds to

 

 

81-2^(2r)  , which is different comparing to original expression. 

 

Can you rewrite the polynomial accurately ...?