Question

How do you find the slope of (4,5) and (9,-10)?

Answer 1

Slope is defined as the difference in `y` per unit `x`

As we don't have units here, we divide the change in `y` by the change in `x`, or in formula (`Delta` means change):
Slope= `(Deltay)/(Deltax)=(y_2-y_1)/(x_2-x_1)=(-10-5)/(9-4)=(-15)/5=-3`

Now we're at it we can also define the whole equation:

Just put in the numbers for one of the points:
`y=ax+b->5=-3*4+b->b=17`
So the equation will be: `y=-3x+17`
graph{-3x+17 [-44.86, 59.17, -26.06, 25.96]}
And you can check your answer against the other point:
`-3x+17=-3*9+17=-10` which is correct.