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Answer:
A.
Step-by-step explanation:
C and D do not create any x² terms when doing the multiplications. so, they are out.
B stands for (a+b)×(a-b) = a² - b².
so, that would give us a "-4" at the end and is not fitting to the "+4" term at the end of the original expression.
that leaves us with A.
let's verify :
(4x+2i)(4x-2i)
it follows the same rule as B :
(a+b)(a-b) = a² - b²
a = 4x
b = 2i
you remember, i = sqrt(-1).
so, we get
(4x)² - (2i)² = 16x² - 4×(sqrt(-1))² = 16x² - 4×(-1) = 16x²+4
bingo !