Multiply.
-$$[ 8 y + ( 8 x + 5 ) ] [ 8 y - ( 8 x + 5 ) ]$$
A) $64 y ^ { 2 } - 64 x ^ { 2 } - 80 x + 25$
B) $64 y ^ { 2 } - 64 x ^ { 2 } + 80 x + 25$
C) $64 y ^ { 2 } - 64 x ^ { 2 } - 40 x - 25$
D) $64 y ^ { 2 } - 64 x ^ { 2 } - 80 x - 25$

Question

Quizplus · Accepted Answer

The expression is a difference of squares: $(a+b)(a-b) = a^2 - b^2$. Here, $a = 8y$ and $b = (8x + 5)$. So, the result is $(8y)^2 - (8x + 5)^2 = 64y^2 - (64x^2 + 80x + 25) = 64y^2 - 64x^2 - 80x - 25$.

Multiply - [8y+(8x+5)][8y−(8x+5)][ 8 y + ( 8 x + 5 ) ] [ 8 y - ( 8 x + 5 ) ][8y+(8x+5)][8y−(8x+5)]

Multiply
- $[ 8 y + ( 8 x + 5 ) ] [ 8 y - ( 8 x + 5 ) ]$