Q19 of 25 Page 8

Find the 4th term in the expansion of (x - 2y)12.


4th term in (x - 2y)12 = T4 = T3 + 1
                              = 12C3(x)12 - 3(-2y)3
     [Tr + 1 in (a + b)n = nCr an – r br]
                              = 12C3(x)9 (-2)3 (y)3
                              =
                              = -1760 x9 y3

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