Question

一道函数小题求大神解答

设f(x)=x+1,当x取什么值时,f(x)等于下列各数:
1/17， 1/2，0.1

Answer 1

f(x)=(x+1-2)/(x+1)=1 - 2/(x+1)
①当1 - 2/(x+1)=1/17时：
-2/(x+1)=-16/17
两边同时约分掉-2：1/(x+1)=8/17
两边同取倒数：x+1=17/8
∴x=9/8
同理：②1 - 2/(x+1)=1/2
-2/(x+1)=-1/2
1/(x+1)=1/4，则x=3
③1 - 2/(x+1)=0.1
-2/(x+1)=-0.9
x+1=20/9，则x=11/9

Answer 2

(1)（x-1）/(x+1)=1/2

2(x-1)=x+1
2x-2=x+1
x=3
(2)（x-1）/(x+1)=0.1
0.1(x-1)=x+1
x-1=10x+10
9x=-11
x=-11/9
(3)（x-1）/(x+1)=1/17
17(x-1)=x+1
17x-17=x+1
16x=18
x=9/8