Question

How do you add `3sqrt50 - 5sqrt18`?

Answer 1

You first try to get any squares from under the root.

You may have noticed that
`50=2*25=2*5^2`
`18=2*9=2*3^2`

We can take these squares out the root (where they are unsquared):

`3sqrt(2*5^2)-5sqrt(2*3^2)=5*3sqrt2-3*5sqrt2`

`=15sqrt2-15sqrt2=0`