My points are -9, (?)
what is the ? please help me understand
Graphing the equation is easy. Usually, with a straight line, the best method is to find out where the line crosses the x and y axes.
For all points on the x-axis, y=0. So, put y=0 into your equation and you find that x=2, so the line passes through the point (2,0).
Similarly to find out where it crosses the y-axis put x=0. That shows that the line passes through the point (0.-9).
Plot those two points and draw in the line that passes through them.
As to the numbers at the end, I assume that they should be written as (-9,?), (-18,-90) and are the co-ordinates of two points on the line, (though why they are significant I don't know). If that happens to be the case, simply substitute x=-9 into the equation to calculate the value of ? .