Answer
No.
Work Step by Step
$f\left( x \right)=4-{{x}^{2}}$
A function is said to be one-to-one if the different inputs have different outputs.
Graphically, no two x values share the same y value if a function is one-to-one.
From the diagram, it is observed that the horizontal line crosses the graph more than once. Therefore, the function $f\left( x \right)=4-{{x}^{2}}$ is not a one-to-one function.
