Question 14732
Consider this:

1) {{{-4x^2 = -4x^2}}} but {{{(-4x)^2 =(-4x)(-4x)}}} = {{{16x^2}}}

So, {{{-4x^2(-4x)^2 = -4x^2(16x^2)}}} = {{{-64x^4}}}

2) {{{(4a^2b^3)^2 = (4^2)(a^2)^2(b^3)^2}}} = {{{(4)(4)(a)^2(a)^2(b)^3(b)^3 = 16(a)(a)(a)(a)(b)(b)(b)(b)(b)(b)}}} = {{{16a^4b^6}}}