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**butterscotchlover2****Member**- Registered: 2017-06-15
- Posts: 2

A portion of the graph of f(x)=ax^3+bx^2+cx+d is shown below.

What is the value of 8a-4b+2c-d?

To view the graph properly, right click the image and click open image in a new tab.

Thanks

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,354

Hi butterscotchlover2

Welcome to the forum.

Hard to tell from the image I am viewing but it looks like the curve crosses the x axis at 0 1 & 2

That would make the function ax(x-1)(x-2)

Also looks like (4,3) is on the curve which will tell you the value of a.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**butterscotchlover2****Member**- Registered: 2017-06-15
- Posts: 2

I am confused, how does (4,3) tell me the value of a.

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**bob bundy****Administrator**- Registered: 2010-06-20
- Posts: 8,354

There are 4 unknowns so, normally, you would need 4 bits of information. The 3 crossing points isn't enough so I looked for a point on the graph. If you put x=4 & y=3 you be able to rearrange to find a. If you then expand the brackets you will be able to find all the unknowns.

Bob

Children are not defined by school ...........The Fonz

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

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**stelii123****Member**- Registered: 2017-06-27
- Posts: 1

4x2 – 4x + 1 = 0

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