f(x+2)=3x平方+2x-1，求f(x-1)
答案:3 悬赏:60
解决时间 2021-02-02 15:36
- 提问者网友：纹身骑士
- 2021-02-01 15:16
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最佳答案
- 二级知识专家网友：一池湖水
- 2021-02-01 16:18
f(x+2)=3x^2+2x-1
设x+2=t
x=t-2
f(t)=3(t-2)^2+2(t-2)-1
=3(t^2-4t+4)+2t-4-1
=3t^2-12t+12+2t-5
=3t^2-10t+7
f(x)=3x^2-10x+7
f(x-1)=3(x-1)^2-10(x-1)+7
设x+2=t
x=t-2
f(t)=3(t-2)^2+2(t-2)-1
=3(t^2-4t+4)+2t-4-1
=3t^2-12t+12+2t-5
=3t^2-10t+7
f(x)=3x^2-10x+7
f(x-1)=3(x-1)^2-10(x-1)+7
全部回答
- 1楼网友：浪女动了心
- 2021-02-01 18:35
f(x+2)=3x^2+2x-1
=3(x+2)^2-12x-4+2x-1
=3(x+2)^2-10x-5
=3(x+2)^2-10(x+2)+15
f(x-1)=3(x-1)^2-10(x-1)+15
=3x^2-16x+28
- 2楼网友：疯山鬼
- 2021-02-01 17:37
f（x+2）=2x-1=2*（x+2）-5
f（x)=2x-5
f（x-1)=2(x-1)-5
f（x)f（x-1)=(2x-5)*[2(x-1)-5]
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