Question

PLEASE help with this APEX question: which of the following expressions is equal to 2x^2+18?

A.(2x-6i)(x-3i)
B.(2x-9i)(x+2i)
C.(2x-6i)(x+3i)
D.(2x-9i)(x-2i)

Answer 1

If you factor 2 from the original expression, you can recognize it as the difference of squares, and factor further accordingly.

... = 2(x^2 +9) = 2(x^2 -(3i)^2)

... = 2(x -3i)(x +3i)

... = (2x -6i)(x +3i) . . . . . matches selection C