Question
Find the equations of all lines having slope -1 that are tangents to the curve 
Solution
The equations of the curve is 
∴ there are two tangents to the given curve with slope – 1 and passing through the points (0, – 1) and (2, 1).
The equation of tangent through (0, – 1) is
y – (– 1) = – 1 (x – 0) or y + 1 = – x or x + y + 1 = 0
The equation of tangent through (2, 1) is
y – 1 = – 1 (x – 2) or y – 1 = – x + 2 or x + y – 3 = 0
