ELI5: Explain Like I'm 5

Fundamental theorem of algebra

The fundamental theorem of algebra says that every polynomial equation with complex coefficients has at least one complex solution. Okay, let's break this down.

First, what's a polynomial? A polynomial is a type of math problem that has variables and numbers, and the variables are raised to different powers (like x^2 or y^3). So, for example, one polynomial equation could be 2x^2 + 3x + 1 = 0.

Next, what are complex coefficients? Complex means something is made up of both real and imaginary parts. So, if we have an equation with complex coefficients, that means it has numbers that have real and imaginary parts. For example, 3 + 2i is a complex number.

Now, what does it mean to have a solution to a polynomial equation? A solution means finding the value of the variable that makes the equation true. So, in the equation 2x^2 + 3x + 1 = 0, the solutions are the values of x that make the equation true. In this case, there are two solutions: x = -1 and x = -1/2.

Finally, the fundamental theorem of algebra says that for any polynomial equation with complex coefficients, there is at least one complex value of the variable (a complex solution) that makes the equation true. This is important because it means that we can always find a solution to a polynomial equation, even if it's a really complicated one.