Answer
$y=0.5x$
Work Step by Step
(Slope-intercept form is y=mx+b)
(Find slope m using $m=\frac{change in x}{change in y})$
$m=\frac{4-2}{2-1}=\frac{2}{1}=2$
(Plug the slope and given data into y=mx+b)
y=mx+b
$1=.5(2)+b$
$1=1+b$
$0=b$
(0 times b is 0, so the final equation is just y=0.5x).
