Well, the general form for point-slope form is y-ysub1= m(x-xsub1). In the general form, ysub1 stands for the y-coordinate and xsub1 stands for the x-coordinate, and m stands for the slope. When writing in point-slope form, we need the slop and one ordered pair.
The equation has already given us two ordered pairs but it doesn't give us the slope. We just need to find the slope between these two points, which is 3/1, or just 3. Then we pick one of the ordered pair they gave us and plug in the general form.
I'll go with the first ordered pair, (2,1). The y and the x in the equation, don't plug them in, leave them as it is, we only need to plug in the slope and the two coordinates. So we get y-1=3(x-2).
I'll only do the first ordered pain for you, and you should be able to do the second one.
If you put it in an equation it would be -7x=7(x+20). You would then -7x to both sides to get -14x=140. Just divide -14 on both sides to isolate x. This equates to -10. If you put -10 back into the equation then it says that 70 is 7 times larger than 10. Which it is.
