Problem: If y=f(x)=x+2x−1y=f(x)=\dfrac{x+2}{x-1}y=f(x)=x−1x+2, then it is incorrect to say:
Answer Choices:
A. x=y+2y−1x=\dfrac{y+2}{y-1}x=y−1y+2
B. f(0)=−2f(0)=-2f(0)=−2
C. f(1)=0f(1)=0f(1)=0
D. f(−2)=0f(-2)=0f(−2)=0
E. f(y)=xf(y)=xf(y)=x Solution:
The value x=1x=1x=1 makes the denominator zero. Since division by zero is not permitted, f(1)f(1)f(1) is undefined, so that (C) is the correct choice.