Hi kobel51,
This DS question is based on Algebra, specifically Classic Quadratics.
We're asked for the value of (a+b)^2, which is the same as asking for the value of a^2 + 2ab + b^2...
Fact 1: ab = 0
This ultimately means that either a or b or both = 0, but this is not enough info to answer the given question.
Fact 1 is INSUFFICIENT
Fact 2: (a-b)^2 = 36
This can be rewritten as a^2 - 2ab + b^2 = 36
It can also be thought of (a-b) = 6 OR -6
Unfortunately, none of this info is enough to answer the given question.
Fact 2 is INSUFFICIENT
Combined, we know that ab=0, so we can plug THAT into the formula from Fact 2 and into the given question:
Fact 2:
a^2 -(0) +b^2 = 36
Given Question:
a^2 - 0 + b^2 = 36
We can answer the given question.
Final Answer: C
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what is a + b squared?
Source: Beat The GMAT — Data Sufficiency |
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When a question throws portions of the common Quadratics your way -- (a+b)^2, (a-b)^2 or (a+b)(a-b) -- you should write out the full equation and fill in what you know in order to figure out what you can solve for. For instance, if we write up the expanded versions of (a+b)^2 and (a-b)^2 side by side, we notice that the difference between the two is 4ab. So starting with (a-b)^2 (from statement 2) we can add 4ab (get its value from statement 1) to find (a+b)^2. the statements are sufficient together. The full solution below is taken from the GMATFix App.
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