Question

    If x + y + z = 6, and x3 + y3 +

    z3 = 36, xyz = 6 then find (xy +yz + zx)?
    A 10 Correct Answer Incorrect Answer
    B 11 Correct Answer Incorrect Answer
    C 22 Correct Answer Incorrect Answer
    D 5 Correct Answer Incorrect Answer

    Solution

    => x3 + y3 + z3 – 3xyz = (x+y+z) (x+y+z)2 – 3(xy +yz + zx) => 36 – 18 = 6 (36 – 3(xy +yz + zx)) => 3 = 36 – 3(xy +yz + zx) => xy +yz + zx = 11

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