(-d + 4) (-d - 4) = 0
-d(-d - 4) + 4(-d - 4) = 0
d² + 4d - 4d - 16 = 0
d² - 16 = 0 2nd choice.
We can find the value of d.
d² - 16 = 0
d² = 16
√d² = √16
d = 4
to check:
(-4+4) (-4 - 4) = 0
0 (-16) = 0
0 = 0
Multiplication property of 0. Any number multiplied by 0 is equal to 0.