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    Question

    If a + b + c = 6, a³ + b³ + c³-3abc =

    342, then what is the value of ab + bc + ca
    A 5 Correct Answer Incorrect Answer
    B 8 Correct Answer Incorrect Answer
    C 7 Correct Answer Incorrect Answer
    D 5 Correct Answer Incorrect Answer

    Solution

    Here is 2 equation and 3 variable Extra variable it can be put anything else = C = 0 A + b = 6, a3 + b3 = 342 Ab = ? = (a +b)3 = a3 + b3 + 3ab (a + b) = 216 = 342 + 3ab × 6 = 18ab = 126 = ab = 7

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