Question

Which expression is equal to 7√28 - 5 √63

A: -√7
B: √7
C: -37√7
D: -11√7

Answer 1

The idea is to try and break those radicands up into 2 numbers multiplied together with one of them being a perfect square. When you do that, this is what you get:
`7 √(4*7)-5 √(9*7)`. In the first radicand, we will pull out the 4 as a 2, and in the second one, we will pull out a 9 as a 3. Then we have
`14 √(7) -15 √(7)` which gives you
`- √(7)`, choice A from above.