#### Answer

$y=-2x + 5$

#### Work Step by Step

RECALL:
The slope-intercept form of a line's equation is $y=mx+b$ where $m$ = slope and $b$ = y-intercept.
With $m=-2$, the tentative equation of the line is $y=-mx+b$.
To find the value of $b$, substitute the x and y coordinates of the given point to have:
$y = -2x + b
\\3=-2(1)+b
\\3=-2+ b
\\3+2=b
\\5=b$
Thus, the equation of the line in slope-intercept form is $y=-2x + 5$.