# How do you find the range of f(x)=10-x^2?

Hence $f \left(x\right) = 10 - {x}^{2} \implies {x}^{2} = 10 - f \left(x\right) \implies 10 - f \left(x\right) \ge 0 \implies 10 \ge f \left(x\right)$
So the range is $\left(- \infty , 10\right]$