# Math Help - year 13 differentiation - please help me

find the values of t when the function defined by
X=4t^3 and y=3t^2-7t is concave up.
give and derivative you need to find when solving this problem .

2. ## Re: year 13 differentiation - please help me

Differentiate twice with respect to x, as directed here: Parametric derivative - Wikipedia, the free encyclopedia.

Set the second derivative greater than zero and solve for values of t.

3. ## Re: year 13 differentiation - please help me

Originally Posted by Damini
find the values of t when the function defined by
X=4t^3 and y=3t^2-7t is concave up.
give and derivative you need to find when solving this problem .
dx/dt=12t^2 dy/dt=6t-7 So dy/dx=(6t-7)/12t^2
Get 2nd derivative using d/dx(dy/dx)=d/dt(dy/dx)*dt/dx
For concave up you want 2nd derivative >0