## Intermediate Algebra for College Students (7th Edition)

$113$
Solve.$(7+8i)(7-8i)$ Need to drop the parentheses and multiply the terms and apply the formula of sum of two multiples such as: $(a+b)(a-b)=a^2-b^2$ $=(7)^2-(8i)^2$ Since, $i^2=-1$ Thus, $=49-64(-1)$ or,$=49+64$ or, $=113$