Chapter 9 - Section 9.5 - Graphs of Quadratic Equations - Exercise Set - Page 665: 18

$\text{$y-$intercept: } 0$

Setting $x=0$ and then solving for $y$, then the $y-$intercept of the given equation, $ y=x^2+8x ,$ is \begin{array}{l}\require{cancel} y=(0)^2+8(0) \\\\ y=0+0 \\\\ y=0 .\end{array} Hence, the $y-$intercept is \begin{array}{l}\require{cancel} \text{$y-$intercept: } 0 .\end{array}