smc

The slope of the line is $\frac{\Delta y}{\Delta x}=\frac{9-1}{3-(-1)}=2$. Using the formula for the point-slope form of a line, we have $y-y_1=m(x-x_1)$, so $y-1=2(x-(-1))\to y-1=2(x+1)$. The x-intercept is the x-value when $y=0$, so we substitute 0 for y: $$0-1=2x+2$$ $$-1=2x+2$$ $$2x=-3$$ $$x=-\frac{3}{2}\to \boxed{-\frac{3}{2}}$$