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C1 Sketching graph kelp

junayd1998

Yh basically i was wondering how you sketch the equation of D I'm unsure do you just put values in for X. Help would be appreciated thanks.

(edited 7 years ago)

Reply 1

Plagioclase

Original post by junayd1998

Yh basically i was wondering how you sketch the equation of D I'm unsure do you just put values in for X. Help would be appreciated thanks.

You should be able to work out where the function crosses the axes (by solving

y=0

and

x=0

respectively) and you should also know the general shape of a cubic graph. From that, you should be able to sketch it.

Reply 2

HapaxOromenon3

Original post by junayd1998

Yh basically i was wondering how you sketch the equation of D I'm unsure do you just put values in for X. Help would be appreciated thanks.

It's a cubic with a positive x^3 coefficient, so you should know the basic shape (if not, look it up).
Since it's given in factorised form, you can see that it will cross the axes at (0,0) and (2,0).
Since there is a double root at x=0 (due to the factor of x^2 rather than just x), this implies that (0,0) will be a stationary point.
Now you should have all the information you need to sketch the graph.

Reply 3

RDKGames

Study Forum Helper

Original post by junayd1998

Yh basically i was wondering how you sketch the equation of D I'm unsure do you just put values in for X. Help would be appreciated thanks.

Well you know the general shape of a cubic, and the equation shows that the cubic has 3 roots at x=0 (repeated) and x=2 so you will need to draw it accordingly to this information.

Reply 4

jamestg

Original post by junayd1998

Yh basically i was wondering how you sketch the equation of D I'm unsure do you just put values in for X. Help would be appreciated thanks.

First of all, think what the graph will look like. If you struggle to from the question, expand the brackets and then see what the highest power is.

Once you know the general shape of the graph, you need to know where it intersects the x and y axis. The most important points to begin with are the x intersections. When y=f(x) intersects the x-axis, y=0, so f(x) must equal 0. If the function in part D equals 0 - how many points will there be and where will they be?

Then you can think about what the y intersection will be. This will be where x=0, so sub that value and whatever y becomes is now your y-intersection.

Finally, plot your graph and label your intersections!