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# Sketching a cubic equation watch

'Sketch y = x^3 + 2x^2 + x'

I'm assuming I'm going to have to factorise to find my roots?

Only problem is I have no idea how to factorise this, anyone got a method for it?

Cheers.
2. (Original post by Tiestar)

'Sketch y = x^3 + 2x^2 + x'

I'm assuming I'm going to have to factorise to find my roots?

Only problem is I have no idea how to factorise this, anyone got a method for it?

Cheers.
take the common factor 'x' out of each term giving x outside the bracket and a quadratic inside.
Then factorise the quadratic giving 3 factors; x(x + a)(x + b)

To sketch you need to know the general shape of cubic functions
You need to solve x(x + a)(x + b) = 0 to find where it crosses the x-axis and may need to know what to do if you have a repeated root

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Updated: November 29, 2011
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