Simplify (x-4)(x-4)(x+7i)(x-7i)

Answer 1

first do the complex conjugates
(x+7i)(x-7i) = x^2 + 49
now the first two terms
x^2-8x+16
now multiply using distributivee property
x^2 ( x^2-8x+16 )
+49 ( x^2-8x+16 )
add