# What is the simplest radical form of #-5sqrt21*(-3sqrt42)#?

##### 1 Answer

Jul 24, 2015

#### Explanation:

The first thing to notice here is that you're multiplying two *negative* numbers, *positive*.

Moreover, using the *commutative property of multiplication*, you can write

ANother important thing to notice here is that *factor* of

This means that the expression becomes

which is equivalent to