Work: 5√2 + √18
First you must find the largest perfect square in √18:
The perfect square happens to be 9
√18 => 9√2
You must then simplify 9 since it is a perfect square:
9√2 => 3√2
Then you must add both terms together:
5√2 + 3√2 = 8√2
Answer: 8√2 or 8 square root 2
I hope this helps you!