Question 118262
 m(the gradient)=vertical distance between the two points/horizontal distance between the two points.
So m=(Y-y)/(X-x) where the two points have coordinates of (X,Y) and (x,y).
So here (X,Y)=(-1,-7) and (x,y)=(1,3).
Hence the gradient m=(-7-3)/(-1-1)=-10/-2=5.
Now the general equation of a straight line is y=mx+c where m is the gradient and c is the y intercept(the y value where the line crosses the vertical Y axis).
So far we have: y=5x+c.(i)
We need to find the value of c.
Since the line passes through (1,3) then we can replace x and y in our equation by 1 and 3 respectively.
This gives (i) as: 3=5*1+c
So 3=5+c
Subtract 5 from each side of the equation and we get: 3-5=c
So c=-2
Hence the required equation is y=5x-2 ANS
(N.B. You should verify your answer by replacing the x by -1 and the y by -7)