y = -1/2x +2 1/2
General equation;
y = mx + c
Calculating the slope;
Change in y/ (change in x) = gradient m
(2-1)/(1-3) = - 1/2
Replacing m gives;
y= -1/2x + c
Calculating the value of c
take point (1,2) above and replace y with 2 and x with 1
2=-1/2 *1 +c
c = 2 1/2
Equation then is
y = -1/2x +2 1/2
