How Do You Solve a Cubic Polynomial with No Rational Roots?

In summary, the conversation discusses the difficulty of solving a degree three polynomial and the use of a graphing calculator. It is mentioned that the polynomial has one irrational root and two complex roots, making it impossible to solve by hand using normal methods. The use of the cubic formula is also mentioned as a possible solution, but it is doubted that a textbook would require its use.
  • #1
ThomasMagnus
138
0
Hello,

I am trying to solve a degree three polynomial, but unfortunately I am stuck

t3+2t2+1=1

This is as far as I can get:
t(t2+2t)+1=0
Where do I go from here?

Thanks!
 
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  • #2
I can get the solution by using my graphing calculator, but I would like to know how to do it by hand :)
 
  • #3
Is the original problem t3+2t2+1=1

or t3+2t2+1=0 ??

You've written down two different things.
 
  • #4
t3+2t2+1=0
sorry :)
 
  • #5
It looks like this polynomial has one irrational root and two complex roots, so it can't be solved by hand (unless you know the cubic formula).
 
  • #6
Yes, it cannot be solved using normal methods. There are no rational roots so synthetic division wouldn't work. Are you sure that it can be solved? Does the back of the book have the answer?

I've never used the cubic formula to solve a polynomial, and I doubt a textbook would require you to do that.
 

FAQ: How Do You Solve a Cubic Polynomial with No Rational Roots?

What is a degree 3 polynomial?

A degree 3 polynomial is a mathematical expression that contains one variable raised to the power of 3 (cubed). It can also be written in the form ax^3 + bx^2 + cx + d, where a, b, c, and d are coefficients and x is the variable.

Why is solving a degree 3 polynomial difficult?

Solving a degree 3 polynomial can be difficult because it involves finding the values of the variable that make the expression equal to 0. This process can be complex and may require the use of algebraic techniques such as factoring, the quadratic formula, or the cubic formula.

What steps are involved in solving a degree 3 polynomial?

The steps involved in solving a degree 3 polynomial include: 1) Identifying the coefficients of the polynomial, 2) Factoring the polynomial, if possible, 3) Using the quadratic formula or the cubic formula to find the roots, 4) Checking the solutions by plugging them back into the original polynomial, and 5) Writing the final solution in factored form or as an equation.

Can all degree 3 polynomials be solved?

Yes, all degree 3 polynomials can be solved using algebraic techniques. However, some polynomials may have complex or imaginary roots, which can make the solution more complicated.

What are some common mistakes to avoid when solving a degree 3 polynomial?

Some common mistakes to avoid when solving a degree 3 polynomial include: 1) Forgetting to check for common factors or to use the GCF (greatest common factor), 2) Making errors when factoring the polynomial, 3) Forgetting to include all possible solutions, and 4) Making errors when substituting values into the original polynomial to check the solutions.

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