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若(2x+1)4 =a0x4 +a1x3 +a2x2 +a3x+a4,试求:(1)a0+a1+a2+a3+a4的值.(2)a0+a2+a4的值.
人气:355 ℃ 时间:2020-02-04 03:22:04
解答
(1)把x = 1代入上式可得:f(1) = (2 +1) 4 = a 0 *1 + a 1 *1 + a 2 *1 + a 3 *1+ a 4 = a 0 + a 1 + a 2 + a 3 + a 4 ,所以a 0 + a 1 + a 2 + a 3 + a 4 = 3 4 = 81 ①; (2)把x = -1代入解析式可得:f(-1) = (-2+ 1) 4 = a 0 *(-1) 4 + a 1 *(-1) 3 + a 2 *(-1) 2 + a 3 *(-1) + a 4 = a 0 –a 1 + a 2 –a 3 + a 4 ,所以a 0 –a 1 + a 2 –a 3 + a 4 = (-1) 4 = 1 ②; 把①+②,可得2a 0 + 2a 2 + 2a 4 = 81 + 1 = 82,所以a 0 + a 2 + a 4 = 41 ; 综上所述,a 0 + a 1 + a 2 + a 3 + a 4 = 81 ,a 0 + a 2 + a 4 = 41 .
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