Just need a little help on these questions. :)

1. The curve C is given by the equation y=mx^{3}-x^{2}+8x+2, for a constant m

A) find dy/dx

The point P lies on C, and has the x-value 5

The normal to C at P is parallel to the line given by the equation y+4x-3=0.

B)find the gradient of the curve at C at P.

Hence find:

C) (I) the value of m,

(ii) the y-value at p.

Just really stuck on this question any help would be brilliant :)

Thanks.

Re: Just need a little help on these questions. :)

please post calculus problems in the calculus forum ... the lobby is for introductions.

Re: Just need a little help on these questions. :)

Quote:

Originally Posted by

**Walshy4119** 1. The curve C is given by the equation y=mx^{3}-x^{2}+8x+2, for a constant m

A) find dy/dx

Okay, what did you get for dy/dx?

Quote:

The point P lies on C, and has the x-value 5

So what are y and dy/dx when x= 5?

Quote:

The normal to C at P is parallel to the line given by the equation y+4x-3=0.

Are you asked to find m so that this is true? The slope of a line perpendicular to a curve, y= f(x), is equal to $\displaystyle -1/f'(x)$. What is the slope of the line y+ 4x- 3= 0?

Quote:

Find the gradient of the curve at C at P.

Okay, that **is** dy/dx evaluated at x= 5.

Hence find:

C) (I) the value of m,

(ii) the y-value at p.

Just really stuck on this question any help would be brilliant :)

Thanks.[/QUOTE]

Re: Just need a little help on these questions. :)

Sorry i posted on the wrong page I'll post it properly now.