Chapter 5, Problem 59RE

In each part, determine the values of $x$ for which $F\left(x\right)$ is positive, negative, or zero without performing the integration; explain your reasoning.

(a) $F\left(x\right)={\displaystyle {\int }_1^x\frac{t^4}{t^2+3}dt}$

(b) $F\left(x\right)={\displaystyle {\int }_{-1}^x\sqrt{4-t^2}dt}$