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
Brent Hanneson - Creator of GMATPrepNow.com
