(2x^2-x-1)^3=a0+a1x+a2x^2+a3x^3+a4x^4+a5x^5+a6x^6
问题描述:
(2x^2-x-1)^3=a0+a1x+a2x^2+a3x^3+a4x^4+a5x^5+a6x^6
(1)a1+a3+a5=
(2)a2+a4+a6=
答
令x=0,得
(2x²-x-1)³=-1=a0
令x=1,得
(2x²-x-1)³=0=a0+a1+a2+a3+a4+a5+a6 ①
令x=-1,得
(2x²-x-1)³=8=a0-a1+a2-a3+a4-a5+a6 ②
两式相加 ①+②,得
2a0+2a2+2a4+2a6=8
a2+a4+a6=5
两式相减 ①-②,得
2a1+2a3+2a5=-8
a1+a3+a5=-4
答:(1)a1+a3+a5=-4
(2)a2+a4+a6=5