(1)6x n+1 -14x n +8x n-1 (2)(x+1)(x+2)(x+3)(x+4)+1 (3)(1-a 2 )(1-b 2 )-4ab (4)8a 3 -b 3 (5)3x 2 +5xy-2y 2 +x+9y-4 (6)2x 2 +xy-y 2 -4x+5y-6 (7)x 2 +x-(a 2 -a)
问题描述:
(1)6x n+1 -14x n +8x n-1 (2)(x+1)(x+2)(x+3)(x+4)+1 (3)(1-a 2 )(1-b 2 )-4ab (4)8a 3 -b 3 (5)3x 2 +5xy-2y 2 +x+9y-4 (6)2x 2 +xy-y 2 -4x+5y-6 (7)x 2 +x-(a 2 -a)
答
(1)6x n+1 -14x n +8x n-1=2x^(n-1)[3x^2-7x+4]=2x^(n-1)(x-1)(3x-4) (2)(x+1)(x+2)(x+3)(x+4)+1=[(x+1)(x+4)][(x+2)(x+3)]+1 =[(x^2+5x)+4][(x^2+5x)+6]+1 =(x^2+5x)^2+10(x^2+5x)+25 =(x^2+5x+5)^2 (3)(1-a 2 ...