Question

Factor completely 81x2-4

Answer 1

(9x + 2)(9x - 2)

Explanation:

To factor this expression, you can use a neat trick called difference of squares.

Difference of squares tells us:

a^2-b^2 = (a+b)(a-b)

Now look at the expression we have here:

81x^2 - 4

well, we know that 81 is 9^2, x^2 is literally x^2, and 4 is 2^2

So we can rewrite this as:

(9x)^2 - 2^2

By difference of squares that gives us:

(9x + 2)(9x - 2)

Answer 2

(9x-2)(9x+2)

Explanation:

81x^2 - 4

Rewriting as

(9x)^2 - 2^2

This is the difference of squares a^2 - b^2 = (a-b)(a+b)

(9x-2)(9x+2)