# Straight line! help

1. Nov 18, 2008

### Run Haridan

Straight line! help!!!

1. The problem statement, all variables and given/known data
the straight line 3y-x-k=0 is the normal to the curve y=4x3+12x2+9x-1 at point A. The curve has two turning points.

a)find the coordinates of A
b)find the coordinates of the turning points of the curve. then, determine whether the turning points are a maximum or a minimum point.

2. Relevant equations
so can we use simultaneous equation on this question?
or maybe replace y in the equation

3. The attempt at a solution
1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

2. Nov 18, 2008

### redargon

Re: Straight line! help!!!

using simultaneous equations will find the points where the curves intersect (this may be in one or more places, so is not necessarily the one you're looking for, but it does help).

What does normal mean and what do you think you would need to find from the straight line in order to find out if it was normalto something?

for b) what is the usual procedure for finding a turning point of a curve?