Mariah,
You will have to play a little detective in gathering your clues based on the formula Ben cited y=mx+b. The "m" is your slope and the "b" is your Y intercept (where X is zero).
Your first step is to solve for Y. Get Y on the left side of the equation and everything else on the right side.
5y = -9x+4
y = (-9x+4) / 5
y = -9/5x + 4/5
The coefficient of X is the slope (-9/5) and slope is rise/run, for every 5 times you go right on your graph, go 9 times down. Positive run you go right, negative run you go left. Positive rise you go up and negative rise you go down.
Your Y intercept (where X is zero) will be the "b" in y=mx+b.
Substitute different numbers for X like X=0, X=5, X=10, X=-5, etc. Why did I suggest 5? Because it will give you whole numbers for Y to work with. You can just as easily substitute X for any other number to get the points to plot your graph.
http://www.purplemath.com/modules/slopgrph2.htm
https://www.mathsisfun.com/equation_of_line.html
Once you plot your graph, use the negative coefficient of X to get its perpendicular line. So instead of -9/5, use the negative of that which gives you 9/5 as the coefficient of X or your slope (m) and then follow the same steps above to plot your line through the graph. The reason I recommend this long way is for you to get a better understanding of how this whole process works. Work is your friend.
Good luck!
Thanks,
-Umar.
