Chapter 4 - Section 4.5 - Finding an Equation from Its Graph - 4.5 Problem Set - Page 238: 8

$y=-2x+3$

The line crosses the y-axis at $y=3$ so $b=3$. Thus, our equation is $y=mx+3.$ Use the point $(1.5,0)$ to substitute into the equation to obtain: $y=mx+3\\0=m(1.5)+3\\-3=1.5m\\-2=m$ Thus the equation is: $y=-2x+3$