Find Expression for Cubic Function: f(1)=6, f(-1)=0, f(0)=f(2)=0

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In summary, a cubic function can be expressed as f(x) = (x+1)(x-2)(x+6) if f(1)=6 and f(-1)=f(0)=f(2)=0. This is because the zeros of a function are also its factors, and by finding the values of x that make the function 0, we can write them as factors in the function's expression. In this case, the factors are (x+1), (x-2), and (x+6), which when multiplied together give us the cubic function.
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DrDanger
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Homework Statement



Find an expression for a cubic function (f) if f(1)=6 and f(-1)=f(0)=f(2)=0

Homework Equations





The Attempt at a Solution


I tried to graph the points and find an equation for the function, but couldn't.
 
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  • #2
Do you know about the relationship between zeros of a function and its factors?
 
  • #3
Bohrok said:
Do you know about the relationship between zeros of a function and its factors?

yeah the factors are the zeros, right?
 
  • #4
Yes. You know what values of x make the function 0, so how do you write the zeros as factors?
 
  • #5
Bohrok said:
Yes. You know what values of x make the function 0, so how do you write the zeros as factors?

(x+1)(x-2)?
 
  • #6
DrDanger said:
(x+1)(x-2)?

You have two; what's the last one?
 
  • #7
Bohrok said:
You have two; what's the last one?
(x+6) lol I have no idea! I know it involves f(1)=6 though
 
  • #8
If your cubic function has a root at x = 0 ( because f(0) = 0), might you write the factor something like (x + 0)? How would you rewrite that factor and put it with the other two factors?
 

FAQ: Find Expression for Cubic Function: f(1)=6, f(-1)=0, f(0)=f(2)=0

What is a cubic function?

A cubic function is a type of polynomial function that has a degree of 3, meaning the highest exponent in the function is 3. It can be written in the form f(x) = ax^3 + bx^2 + cx + d, where a, b, c, and d are constants.

How do I find the expression for a cubic function when given specific points?

To find the expression for a cubic function when given specific points, you can use the method of interpolation. This involves setting up a system of equations using the given points and then solving for the coefficients a, b, c, and d. These coefficients will then make up the expression for the cubic function.

What does f(1)=6, f(-1)=0, f(0)=f(2)=0 mean?

This notation represents the given points on the cubic function. For example, f(1)=6 means that when x=1, the value of the function f(x) is equal to 6. Similarly, f(-1)=0 means that when x=-1, the value of the function is 0. The notation f(0)=f(2)=0 means that when x=0 or x=2, the value of the function is also 0.

Can I graph a cubic function with only these three points?

Yes, you can graph a cubic function with only these three points. Since a cubic function has a degree of 3, it will have a curve with two turning points. By plotting the given points and connecting them with a smooth curve, you can graph the cubic function.

Are there any other ways to find the expression for a cubic function?

Yes, there are other ways to find the expression for a cubic function. One method is to use the method of extrapolation, where you use the given points and an additional point to solve for the coefficients. Another method is to use the method of least squares, where you find the line of best fit for the given points and use that line to find the expression for the cubic function.

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