Question

Please answer and explain your reasoning thanks!

Answer 1

The first one is the correct answer.
When you multiply, you end up with 49x^16+28xy^40-28x^40 -16y^64
The two middle terms cancel out so you end up with 49x^16-16^64.

Answer 2

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

This formula will be useful in helping us factor this.

$49x^{16}-16y^{64}$

This is the equation that we are going to factor.
Let's first change this equation to have the form $a^2-b^2$

In order to do that, here are two important exponent rules that was used.
$(a^b)^c=a^{bc}$
$(ab)^c=a^c b^c$

With those rules, we can change the equation into the following:
$(7x^8)^2-(4y^{32})^2$

Refer back to the formula I showed in the beginning of this answer.
$a^2-b^2=(a-b)(a+b)$

$(7x^8)^2-(4y^{32})^2=(7x^8-4y^{32})(7x^8-4y^{32})$

Thus, your answer is the first choice. Hope this helps! :)