Q&A #1576

Teachers' Lounge Discussion: Graph sketching

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From: Tasha

To: Teacher2Teacher Public Discussion
Date: 2006071909:13:14
Subject: Re: Gradient on curves


If y=x^3 (X^3  means x cubed)
Then firstly you need to draw a graph.
Include a point on the x axis that is called x+(delta x)
and on the y axis add a point called (x^3+deltax)^3

Then work out the y co-ordinate which is
x^3+3x^2(delta x)+3x(delta x)^2+(delta x)^3

then work out the step:
3x^2(delta x)+3x(delta x)^2+(delta x)^3
divide it by the rise:
(delta x)

and the gradient is 3x^2

the general rule when y=x^n
that the gradient is Nx^n-1

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