



 
Hi Suez. The equation of a parabola is in the form: where A, B and C are undetermined constants. So when you take the derivative of both sides with respect to x by using the chain rule, you get: d/dx ( y  A) = d/dx ( B ( x  C )^{2} ) dy/dx = B d/dx ( x  C )^{2} dy/dx = B (2)(x  C) d/dx (x  C) dy/dx = 2Bx  2BC This, as we expected, is a linear equation (no squared terms) that describes the tangent line to the parabola. You should know that the slope of the parabola (the tangent line) is simply dy/dx, so you can 6 = 2B(1)  2BC Now there are two unknowns in two equations, which you can solve in any of the usual ways. Once you know B and C, you can substitute them into the original expression along with the coordinates of the point Hope this helps,  


Math Central is supported by the University of Regina and The Pacific Institute for the Mathematical Sciences. 