Question: Product with Roots

Comment on Product with Roots

I did this a slightly different way and still got A. I didn't know the rule: x>0, then (√x)(√x)=x. So I did, (√49-√14+√14-√4) to get 7-2 = 5, and then √9-√3+√3-1 to get 3-1=2. Then I multiplied (5)(2) to get 10. So if x>0, can we also do (√x)(√x) = √(x)(x)? Thanks!
gmat-admin's picture

Yes, that rule is definitely accurate. It's very similar to √(xy) = (√x)(√y)

I solved it using the different of two squares rule and came up with the right answer.

Is it correct?
gmat-admin's picture

That's a perfectly valid approach. In fact, I think it's the best approach.

I don't cover that approach here, because the practice question appears very early in the module (just after the FOIL method video), so we haven't yet covered differences of squares.

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