81-49n^4 difference of two squares?

Hi,
Short Answer: (9-7n)(9+7n)

Comments:
As others have said, this is the difference of two squares. Here's a quick way to factor it:
Take the square root of each term and write these roots in two sets of parentheses like this:
(9 7n)(9 7n)
Now, put a + sign in one binomial and a negative in the other. It doesn't matter whether the positive sign goes in the first or second binomial. So, you get this either this:
(9-7n)(9+7n) or this: (9+7n)(9-7n). They are both equally correct.

Hope this helps.
FE

81 – 49n⁴ = (9)² – (7n²)²
.............. = (9 + 7n²)(9 – 7n²)

Difference Of Two Squares

a^2 - b^2 ≡ (a + b)(a - b)

81 - 49n^4
= 9^2 - (7n^2)^2
= (9 + 7n^2)(9 - 7n^2)

( 9 - 7 n ² ) ( 9 + 7 n ² )

Yes it is
-(7n^2-9) (7n^2+9)

this is an example of a difference of two squares.

factor this out to verify to yourself that this equation is indeed a difference of two squares

(81-49n^4) =

(9-7n^2)(9+7n^2) ---> proof that this is an example of the difference of two squares