Data Sufficiency (DS) | Re: What is the value of x^2 – y^2 ?

Target question: What is the value of x² – y² ?

Statement 1: x + y = 2y – 1
Subtract 2y from both sides to get: x - y = -1
There are several values of x and y that satisfy statement 1. Here are two:
Case a x = 0 and y = 1, in which casex² – y² = 0² – 1² = 0 - 1 = -1
Case b x = 1 and y = 2, in which casex² – y² = 1² – 2² = 1 - 4 = -3
Since we cannot answer thetarget question with
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