Question

How do you simplify `-5sqrt21*-3sqrt42`?

Answer 1

You can write your product as:
`[-5sqrt(7*3)]*[-3sqrt(7*6)]=`

`=[-5sqrt(7)sqrt(3)]*[-3sqrt(7)sqrt(6)]=`

`=[-5sqrt(7)sqrt(3)]*[-3sqrt(7)sqrt(3)sqrt(2)]=`

Multiplying:

`=15*7*3*sqrt(2)=315sqrt(2)`