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Plugging in values I get 15/4 - 4/5 which equals to 59/20

I think the trick is knowing that sqrt(y-1)^2 must be solved inside the parentheses first, before squaring the inside, then taking its square root. If you just have the powers cancel first, you would get 15/4 - (-4/5), thus equaling 91/20 the wrong answer.

Plugging in values I get 15/4 - 4/5 which equals to 59/20

I think the trick is knowing that sqrt(y-1)^2 must be solved inside the parentheses first, before squaring the inside, then taking its square root. If you just have the powers cancel first, you would get 15/4 - (-4/5), thus equaling 91/20 the wrong answer.

Btw, I dont think 91/20 is a wrong answer... Its just not one of the answer choices here. So we were left to find one of more possible right answers.