## College Algebra (6th Edition)

$18-12i$
FOIL the terms in the parentheses, and then combine like terms. Be sure to turn $i^2$ into $-1$. $(4-i)^2-(1+2i)^2$ $(4-i)(4-i)-(1+2i)(1+2i)$ $16-4i-4i+i^2-(1+2i+2i+4i^2)$ $16-8i-1-(1+4i+4i^2)$ $15-12i-1+4$ $18-12i$