Question

When multiplied, what is the simplified form of (5 − 2i)(1 − 2i)? Write the answer in standard form, a + bi, where a and b are real numbers.

Answer 1

(5 - 2i)(1 - 2i) You can solve this as though it was (x - 2)(x + 3): use foil

F: 5*1 = 5
O: 5 *(-2i) = - 10i
I : -2i * (1) = - 2i
L: (-2i)(-2i) This may take a bit. There's a few signs hanging around.
L: (-2 * -2)*(i * i)
L: 4 (i *i)
L: 4(-1)
L: - 4 So combine these results.

FOIL: 5 - 10i - 2i - 4 Group the like terms
FOIL: 5 - 4 - 10i - 2i Now collect them
FOIL: 1 - 12i <<<<<<< Answer