Let the required equation be
y = mx + c ......(1)
Since (1) goes through the first point, we have
3 = -m + c, so that c = m + 3.
Hence (1) becomes
y = mx + m + 3 ........(2)
If in addition the line goes through the second point, we have
-2 = 4m + m + 3, so that m = -1.
Hence (2) becomes
y = -x + 2, i.e. x + y = 2.
Or, again, using the result of the last article the equation is
