Question

    If x = 21, then the value of x5 -

    22x4 + 22x3 - 22x2 + 22x - 1 is
    A 10 Correct Answer Incorrect Answer
    B 20 Correct Answer Incorrect Answer
    C 11 Correct Answer Incorrect Answer
    D 14 Correct Answer Incorrect Answer

    Solution

    Given expression :  x 5 - 22x 4 + 22x 3 - 22x 2 + 22x - 1 = x5 - 21x 4 - x4 + 21 x 3 + x3 - 21 x2 - x2 + 21 x + x - 1 = x5 -x5 -x4 + x4 +x3-x3-x2+x2+21 -1 [given that x = 21] = 21-1 = 20

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