Differentiation Problem

The problem

The Diagram shows the graph of y=x^3-12x+17
A is the maximum point on the curve
C is the minimum point on the curve
The curve crosses the y axis at B

For the equation find dy/dx, y=x^3-12x+17 (DONE)

Heres the problem

find the gradient of the curve at B

now what am I supposed to do here?

this is what i tried but im not sure if its right

3x^2-12=17

make x the subject therefore giving

x=$$\sqrt{}29/3$$

so is that right or..?
 Blog Entries: 9 Recognitions: Homework Help Science Advisor For b) you need to find the value of the derivative at the point B. What are the coordinates of the point B ?
 im guessing the coordinates at point B are (0,17), but how does that help me in finding the gradient at that point

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Differentiation Problem

 Quote by tigerd12 The problem The Diagram shows the graph of y=x^3-12x+17 A is the maximum point on the curve C is the minimum point on the curve The curve crosses the y axis at B For the equation find dy/dx, y=x^3-12x+17 (DONE) Heres the problem find the gradient of the curve at B now what am I supposed to do here? this is what i tried but im not sure if its right 3x^2-12=17
I presume you found that the derivative is 3x^2- 12. By why are you asserting that the derivative is 17? You are supposed to be finding the value of the derivative!

 make x the subject therefore giving x=$$\sqrt{}29/3$$ so is that right or..?
No, it's not right- you weren't even asked for a value of x!

You know that f'(x)= 3x^2- 12. You are asked to find its value at point B. Of course, to do that you need to know what x is there. Saying the graph crosses the x-axis tells you that y= 0. Okay y= x^3- 12x+ 17= 0. Can you determine what x is from that?

 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution

 Quote by HallsofIvy You know that f'(x)= 3x^2- 12. You are asked to find its value at point B. Of course, to do that you need to know what x is there. Saying the graph crosses the x-axis tells you that y= 0. Okay y= x^3- 12x+ 17= 0. Can you determine what x is from that?
Sorry, I don't seem to be understand what you are saying. Do you want me to find the solutions of the equation x^3-12x+17?
 Remember. The curve crosses y-axis at point B. So you know the y = 0 but you have to find the x-value for the point B: In other words. B = (x,0) Also, you know that f'(x) = 3x^2-12 Let f'(x) = 0 and then find a value for x. Then you have got point B! :)

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