SSC CPO SI and ASI Model Paper 5

Question : 101 of 200

Marks: +1, -0

If a + b = 13 and a3 + b3 = 637, then what is the value of ab?

Solution:

(3)

a + b = 13; and a^3 + b^3 = 637

By cubing a + b = 13;

a^3 +b^3 + 3ab(a +b) = 2197

⇒ 637 + 39ab = 2197
⇒ 39ab = 1560
⇒ ab = 40

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