The range of the function f(x)=9-x2 is
(1)
Let y=9-x2⇒y2=9-x2
⇒x2=9-y2⇒x=9-y2
Clearly, 9-y2≥0⇒y2≤9⇒-3≤y≤3
But y≥0. Hence, 0≤y≤3