Well for part (a) since the equation of a slope is then the expression should be right?You can find the slope of thetangent lineto a parabola at a point using the following method.

(a) Find an expression, in terms of x and a, for the slope of asecant linefrom to another point on the parabola.

(b) Simplify this slope assuming . What number, in terms of , does this quantity approach as approaches ?

I don't understand part (b) at all.