Question

Which of the following is not a function?

• A. $\{(x,y):x,y\in R,x^2=y\}$
• B. $\{(x,y):x,y\in R,y^2=x\}$
• C. $\{(x,y):x,y\in R,x=y^3\}$
• D. $\{(x,y):x,y\in R,y=x^3\}$

Answer 1

Answer: (B)

$\because$ $y^2=x\Rightarrow y=\pm \sqrt{x}$
is one value of x gives two values of y. So,
$\{(x,y):x,\in R,y^2=x\}$
is not a function.