Vincen wrote:What is the value of r² − 2rs + s²?
(1) s = 4
(2) r − s = 12

Target question: What is the value of r² − 2rs + s²?
This is a good candidate for rephrasing the target question.
Aside: Here's a video with tips on rephrasing the target question: https://www.gmatprepnow.com/module/gmat- ... cy?id=1100

Notice that r² − 2rs + s² is one of the special quadratic expressions
It can be factored as follows: r² − 2rs + s² = (r - s)(r - s) = (r - s)²
So....REPHRASED target question: What is the value of (r - s)² ?

Statement 1: s = 4
Since there's no information about r, there's no way to determine the value of (r - s)²
Since we cannot answer the REPHRASED target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: r − s = 12
PERFECT!!
This means that (r - s)² = (12)² = 144
Since we can answer the REPHRASED target question with certainty, statement 2 is SUFFICIENT

Answer: B

Cheers,
Brent