Chapter 10 - Radical Expressions and Equations - 10-3 Operations With Radical Expressions - Practice and Problem-Solving Exercises - Page 629: 15

$-7\sqrt 5$

You are given $3\sqrt 45$ $-$ $8\sqrt 20$.Simplify: Factor perfect squares out of the radicands: $3 \sqrt 9*5$ $-$ $8 \sqrt 4*5$ Multiplication property: $3 (\sqrt 9) ({\sqrt 5})$ $-$ $8 (\sqrt 4) ({\sqrt 5})$ $3(3) (\sqrt 5)$ $-$ $8(2) (\sqrt 5)$ $9\sqrt 5$ $-$ $16\sqrt 5$ $\sqrt 5(9-16)$ =$-7\sqrt 5$