If two of the four expressions x+y, x+5y, x-y, and 5x-y are chosen at random, what is the probability the their product will certainly be the the kind of x² – by², wherein b is one integer?

(A) 1/2

(B) 1/3

(C) 1/4

(D) 1/5

(E) 1/6

Be at sight comfortable with difference of squares. You’re almost guaranteed to require it on your GMAT. You need to recognize it forwards, backwards, and upside-down. There isn’t much content you require to recognize for the GMAT quant but in order to be repetitively successful so the you can go in over there on check day and also snag your 700+ score girlfriend need complete fluency with that limited content. On this one we’re trying to find a product of two terms that will create difference that squares. For this reason we need something in the format: (x+y(x-y). There’s just one pairing that offers us the best format. Now you have to figure out what that means in terms of probability. In general, probability is certain scenario/total scenarios. You can calculate the total and the certain scenarios making use of the slot method. How many teams of 2 deserve to you do from four things? (4*3)/(1*2) = 6. So that’s her denominator. And also then there’s only one team the works, the pairing of (x + y)(x – y). Therefore that pipeline you v 1/6. E. In-depth diagrams below and an in depth video clip explantation here: If 2 of the four expressions


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