f(x) = ax˛ + bx + c. If f(1) = 6, f (-1) = 8, f(-2) = 18, find f (2)

Can someone please do the solution for me. I know that the answer is 14 but I dont know how to get that.

Thanks!

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- Dec 8th 2009, 11:48 AM #1

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- Dec 8th 2009, 11:51 AM #2

- Dec 8th 2009, 12:01 PM #3

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- Dec 8th 2009, 12:07 PM #4

- Dec 8th 2009, 12:08 PM #5

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the first time, you need find a, b, c:

we have $\displaystyle f(1)$so $\displaystyle x=1$ and change into the $\displaystyle f(x)=ax^2+bx+c$

then $\displaystyle f(-1) and f(-2)$ is same the$\displaystyle f(1)$

so we have

$\displaystyle a+b+c=6$

$\displaystyle a-b+c=8$

$\displaystyle 4a-2b+c=18$

you can find a, b,c

then change a, b, c you found go into $\displaystyle f(x)=ax^2+bx+c$

finally $\displaystyle f(2)$ you can find easily.

if you didnot understand you can ask me and i can explain again. sorry my english bad something i wrote wrong .

- Dec 8th 2009, 12:10 PM #6

- Dec 8th 2009, 12:16 PM #7

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- Dec 8th 2009, 12:27 PM #8

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- Dec 8th 2009, 12:39 PM #9

- Dec 8th 2009, 12:52 PM #10

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