# How to get Formula from a Cubic Graph

1. Jan 12, 2010

### Jordash

1. The problem statement, all variables and given/known data

The figure shows the graph of a cubic polynomial.

The function graphed is f(x)=

Hint: You may write the function as f(x) = a(x-b)(x-c)(x-d) where b, c, and d, are integers and a is a fraction.

2. Relevant equations

3. The attempt at a solution

I'm lost...

2. Jan 12, 2010

### rock.freak667

When f(x)=0 the graph cuts the x-axis, so what are the values of b,c and d?

3. Jan 12, 2010

### Dick

b, c and d are where f(x)=0, can't you read those off from the graph? Now what about a?

4. Jan 12, 2010

### Jordash

5. Jan 12, 2010

### rock.freak667

Are you unable to read the number off of the graph? Which part made no sense?

6. Jan 13, 2010

### Staff: Mentor

Simply by observing the graph you should be able to find b, c, and d in your equation f(x) = a(x -b)(x - c)(x - d).

And you should be able to get a by noticing where the graph crosses the y-axis.