## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$\text{(b) }y=2x$
The graph contains the points $(0,0)$ and $(4,8)$. Both points satisfy the equation $y=2x$. $0=2(0)$ $8=2(4)$ Thus, the equation of the line is $y=2x$.