If a3 + b3 = 218 and a + b = 2, then the value of √1-ab is :
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 6
a3 + b3 = (a + b)(a2 + b2 - ab)
a3 + b3 = (a + b)[(a + b)2 - 3ab)]
218 = 2[(a + b)2 - 3ab)]
218/2 = 22 - 3ab
109 = 4 - 3ab
-3ab = 109 – 4 = 105
ab = -105/3 = -35
√1-ab = √1-(-35) = √36 = 6