Answer
See explanations.
Work Step by Step
Step 1. Given $f(x)=x^5+2x^4+x^3+3$, for $x=-1.8$, we have $f(-1.8)=(-1.8)^5+2(-1.8)^4+(-1.8)^3+3=-0.73248\lt0$
Step 2. For $x=-1.7$, we have $f(-1.7)=(-1.7)^5+2(-1.7)^4+(-1.7)^3+3=0.59263\gt0$
Step 3. As $f(-1.8)$ and $f(-1.7)$ have opposite signs, based on the intermediate value theorem, there is a real zero between -1.8 and -1.7.