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Definite intergration area under curve bounded with line

by thomas49th
Tags: bounded, curve, definite, intergration, line
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May25-08, 01:31 PM
P: 656
1. The problem statement, all variables and given/known data

A cruve has the equation [tex]y = x{3} - 8x^{2} + 20x [/tex]. The curve has stationary points A and B. There is a line through B parallel to y axis and meets the x axis at the point N. The region R is bounded by the curve , the x-axis and the line from A to N. Find the exact area under the curve

2. Relevant equations

3. The attempt at a solution

Well I found the x co-ords of A and B, which is [tex]\frac{10}{3}[/tex] or 2. I intergrated the curve and got

[tex]\frac{4x^{3}}{4} - \frac{8x^{3}}{3}+10x^{2}[/tex]

no +C as we'll be having limits i presume

But i dont know how to get the area of region R... as there is a stupid line in the way!!!

Can somebody show/help me to do it.

Thanks :)
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May25-08, 02:11 PM
P: 64

My first advice is to a picture of your problem. After that you notice that the exercise is to calculate the integral from x=A to x=B of f, i.e. integration of a polynomial. I expect you know how to do that.
May25-08, 03:51 PM
P: 656
i can intergrate a polynominal easily and in the question paper there is a picture of the question. But because of this AN line, it's thrown me. How would you go about doing it.


May25-08, 07:07 PM
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tiny-tim's Avatar
P: 26,151
Definite intergration area under curve bounded with line

Hi thomas!

If I've understood the question right, all you have to do is add a triangle (whose area is obvious), and you get the standard integral.
May26-08, 07:37 AM
P: 656
ahhh i see cheerz :)

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