lgarces19 wrote:

If k and m are numbers such that k + m = 20 and k^2 + m^2 = 289, then the value of the product km is

(A) between 20 and 60

(B) between 60 and 100

(C) between 100 and 150

(D) between 150 and 200

(E) greater than 200

Bunuel's solution is perfect.

I just want to point out that there's no shortage of questions that test the concepts tested here.

Important expansions:

(x + y)² = x² + 2xy + y² and

(x - y)² = x² - 2xy + y² So, if you see questions that include information about x² + y² and 2xy (or just xy), then you should consider their relationship with the above expansions.

Cheers,

Brent

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Brent Hanneson – GMATPrepNow.com

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