Let the sum of the coefficients of the (5x12 − x13) n expansion be m, the sum of the binomial coefficients be n, and M-N = 992, then the coefficients of the X2 & nbsp; term in the expansion are () A. 250B. -250C. 150D. -150

Let the sum of the coefficients of the (5x12 − x13) n expansion be m, the sum of the binomial coefficients be n, and M-N = 992, then the coefficients of the X2 & nbsp; term in the expansion are () A. 250B. -250C. 150D. -150

Let x = 1 give M = 4N, then n = 2n, ∵ M-N = 992, ∵ 4n-2n = 992, let 2n = k, then k2-k-992 = 0, ∵ k = 32, ∵ n = 5, ∵ tr + 1 = c5r (5x12) 5 − R (− x13) r = (- 1) r · c5r · 55-r · x15 − R6, let 15 − R6 = 2, then r = 3, ∵ x2 coefficient is (- 1) 3c53 · 52 = - 250, so the option is B

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