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Mclaughlin
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help me!
Source: Beat The GMAT — Data Sufficiency |
I think the answer is D.
ab^2=50, a (a^2 - b^2) = a^3 - ab^2
Statement I
a^3 = 8
8 - 50 = -42
Sufficient.
Statement II
ab=-10
ab^2=50
b=-5, a= 2
8-50= -42
Sufficient.
Hence Answer is D.
Whats the OA?
ab^2=50, a (a^2 - b^2) = a^3 - ab^2
Statement I
a^3 = 8
8 - 50 = -42
Sufficient.
Statement II
ab=-10
ab^2=50
b=-5, a= 2
8-50= -42
Sufficient.
Hence Answer is D.
Whats the OA?
Since it's a data sufficiency question, we only need to figure out "a" and "b." In this specific question, we don't even need to simplify that equation in the stem.
(2) might strike people as "the complicated one." ab = -10 and we already know ab^2 = 50. Compare ab^2 and ab. ab^2 = (-5) ab. Set equal to zero: ab^2 + 5ab = 0 ==>> simplify into ab * (b + 5) = 0 and we already know that ab = -10, not zero. That leaves b = -5 as the only solution. a = +2. Since you've identified a & b, (2) is sufficient.
(2) might strike people as "the complicated one." ab = -10 and we already know ab^2 = 50. Compare ab^2 and ab. ab^2 = (-5) ab. Set equal to zero: ab^2 + 5ab = 0 ==>> simplify into ab * (b + 5) = 0 and we already know that ab = -10, not zero. That leaves b = -5 as the only solution. a = +2. Since you've identified a & b, (2) is sufficient.
