How can I factor a cubic function with a given x-intercept?

In summary, to determine the x-intercepts of the given function y=x^3+2, you can solve for when y=0. This leads to x=-\sqrt[3]{2}. There is no need to factor, but if you do, the resulting factors will be of the form (x+\sqrt[3]{2})(x^2+ax+\sqrt[3]{4}).
  • #1
Calcuconfused
1
0
Alright, so I need a little brush up on my pre calc apparently! I need to determine the x-intercepts of the following function.

y=x^3 + 2

I know I need to factor it... I'm just not completely sure how! Thanks!
 
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  • #2
There's no need to factor. The x-intercepts are when y=0, so you just need to solve the equation:

[itex]0=x^3+2[/itex]
 
  • #3
Calcuconfused, If you move the 2 onto the other side of [itex]0=x^3+2[/itex] and then take the cube root of both sides, you'll end up with [tex]x=-\sqrt[3]{2}[/tex] so if you were to try and factor it (in case you need to find the factors for another purpose, such as to show what all 3 roots are) you're going to have an ugly thing to factor.

But regardless, if you need to factor it, you'll end up with a linear factor and a quadratic factor, and since we've already shown one of the roots, the end result will be of the form

[tex]\left(x+\sqrt[3]{2}\right)\left(x^2+ax+\sqrt[3]{4}\right)[/tex]

For some yet to be found constant value a.
 

1. What is a cubic function?

A cubic function is a polynomial function of degree 3, meaning that the highest exponent of the variable is 3. It can be written in the form f(x) = ax³ + bx² + cx + d, where a, b, c, and d are constants.

2. Why is factoring a cubic function important?

Factoring a cubic function helps to find its roots or solutions, which are the values of x that make the function equal to 0. This is useful in solving real-world problems and understanding the behavior of the function.

3. What are the different methods for factoring a cubic function?

The most common methods for factoring a cubic function are the grouping method, the difference of cubes formula, and the rational zero theorem. The method to use depends on the coefficients of the cubic function.

4. How do you factor a cubic function using the grouping method?

The grouping method involves grouping the terms of the cubic function into two pairs and factoring out the greatest common factor of each pair. Then, factor out the greatest common factor of the resulting expressions to obtain the final factored form.

5. Can all cubic functions be factored?

No, not all cubic functions can be factored. Some cubic functions have irrational or complex roots, which cannot be factored using rational numbers. However, using the rational zero theorem, we can determine if a cubic function has at least one rational root and then use other methods to factor it.

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