Functions Modeling Change: A Preparation for Calculus, 5th Edition

(a) $f(0)=-4$ (b) $t = \pm 2$
(a) To find $f(0)$, evaluate the function at $t=0$ to get $f(0)=0^2-4=-4$. (b) Using $f(t)=0$, the following equation is created: $$t^2-4=0$$ Add $4$ to each side to get $$t^2=4$$ Take the square root of each side, yielding a plus or minus sign, to get $$t=\pm 2$$