consider the equations of the cubic function and the straight line.
The straight line crosses the cubic function at point A(-1,0). Suppose that the straight line crosses the cubic function at two further points P( ) and Q ), where .
1. Show that
2. Hence find the equation of the line throught the point A tangent to the cubic function at a point distinct from the point A
Slight warning: when Grandad says " For question (1), say that their sum = " and "For question (2), say that they must be equal if the line is tangent; so ", he is referring to the "a, b, c" in the general quadratic, , not the "a" in this particular equation, y= ax+ a.