Finding Gradients of Curves

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Finding Gradients of Curves

Introduction

I am going to investigate the gradients of different curves and try to

work out a pattern that I could use to find the gradient of any curve.

I will draw graphs of a selection of curves, some by hand, some using

Autograph and some using Excel. I will use three methods to

investigate the graphs. Firstly, I will draw tangents to the curves at

4 or 5 points and measure the gradients. Secondly, I will draw chords

between x = 1 and 4 or 5 points and measure the gradients. Thirdly, I

will use algebra to work out a formula for the gradient and see how

this matches the first two methods.

At first I split up the coursework into 3 main families (for each

family there are additional equations to investigate):

Part One: Curves involving x2

1. y = x2

2. y = 2x2

3. y = 3x2

4. y = 4x2

5. y = x2 + 1

6. y = 7x2 + 6

Part Two: Curves involving x2 + x

1. y = x2 + x

2. y = x2 + 2x

3. y = 7x2 + 4x + 5

Part Three: Curves involving x3 + x

1. y = x3

2. y = 2x3

3. y = 4x3 + 2x - 5

Finally, I will summarise my results in a series of tables and work

out an overall formula that I could use to predict the gradient of any

curve.

PART ONE: CURVES CONTAINING X2

(1) y = x2

I am investigating the changes in gradient for the curve y = x2. To

plot the curve, I will use the table of values given below.

x

0

1

2

3

4

5

6

y

0

1

4

9

16

25

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