rohitd80 wrote:

Hi Bunuel,

I understand your explanation.

I wanted to apply the mod and solve this problem, However, we also know that..."When the GMAT provides the square root sign for an even root, then the only accepted answer is the positive root".

So, the solution to this problem can go either way 87/20 (considering the positive roots only) or 63/20 ( with the mod approach) ...

PEMDAS

parentheses comes first. we cannot jump operations and square/take the square root of everything before solving for what is in parenthesis.

y-1 results in a negative expression. After squaring it, it gives us a positive expression. Moreover, after squaring everything, the square root will be as well a positive number. I did not do the way bunuel explained, yet I got to the right answer.

sqrt[(x+3)^2] = sqrt[(3/4+12/4)^2] = sqrt[(15/4)^2]. this will result in 15/4.

now let's take y

sqrt[(y-1)^2] = sqrt[(2/5-5/5)^2] = sqrt[(-3/5)^2]. now, if we square -3/5 we get 9/25 which is a positive number. sqrt of 9/25 is 3/5.

we got 15/4 - 3/5

multiply first by 5/5 and second by 4/4, the result is:

(15*5)/20 - (3*4)/20. extend this and get: (75-12)/20.

the result is 63/20.