Answer to Question #173797 in Algebra for Festus

Question

(x - 2)(x - 2i)(x + 2)(x - 2i) is equal to

Answer 1

$$(x - 2)(x - 2i)(x + 2)(x - 2i)$$

$$=(x^2-4)(x^2-4i-4)$$

$$=x^4-4x^2i-4x^2-4x^2+16i+16$$

$$=x^4-8x^2 +16-(4x^2-16)i$$