SOLUTION: Question: √ 80 -2 √ 20 + 3 √ 45 Please answer step by step. Answer in book: 9 √ 5 My answer: 10 √5

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Question 812325: Question: √ 80 -2 √ 20 + 3 √ 45
Please answer step by step.
Answer in book: 9 √ 5
My answer: 10 √5
Answer by richwmiller(17219) About Me  (Show Source):
You can put this solution on YOUR website!
√ 80 -2 √ 20 + 3 √ 45=
sqrt(80)-2*sqrt(20)+ 3*sqrt(45)=
sqrt(4*4+5)-2*sqrt(4*5)+ 3*sqrt(3*3*5)=
4Sqrt(5)-4sqrt(5)+9 sqrt(5)=
(4-4+9)Sqrt(5)=
9*sqrt(5)