ELI5: Explain Like I'm 5

Properties of polynomial roots

Polynomials are simply fancy math equations that involve lots of different terms with different powers of x in them. The roots of a polynomial are the special numbers that make the whole equation equal to zero.

For example, let's say we have the polynomial equation:

5x^2 + 8x + 3 = 0

To find the roots of this equation, we need to solve for x. We can use the quadratic formula for this, which is a special equation that helps us find the roots of any quadratic polynomial.

The quadratic formula looks like this:

x = (-b ± √(b^2 - 4ac)) / 2a

(b, a, and c are just different numbers from our polynomial equation)

If we plug in the numbers from our example equation, we get:

x = (-8 ± √(8^2 - 4(5)(3))) / (2(5))

Simplifying this equation gives us:

x = (-8 ± √(4)) / 10

x = (-8 ± 2) / 10

Now we have two possible roots:

x = (-8 + 2) / 10 = -3/5
or
x = (-8 - 2) / 10 = -4/5

These two numbers are the roots of our polynomial equation.

But what do we mean when we talk about the properties of polynomial roots? Well, one thing we can look at is the number of roots that a polynomial equation has.

For example, a quadratic polynomial like the one we just solved always has two roots (unless both roots end up being the same number). A cubic polynomial (with a highest power of x^3) can have either one or three roots, and a quartic polynomial (highest power of x^4) can have up to four roots.

Another property of polynomial roots is that they can sometimes be complex numbers. This means they involve a combination of real numbers and imaginary numbers (which involve the square root of -1). Complex roots often come in pairs (called conjugate pairs) that involve the same real number but different imaginary numbers.

For example, a cubic polynomial might have one real root and two complex conjugate roots, like this:

x^3 - 2x^2 + x + 2 = 0

One root is x = 2, which is a real number. The other two roots are complex conjugate pairs:

x = 1 + i
x = 1 - i

(The "i" just represents the imaginary number, which is the square root of -1.)

So, in summary, the properties of polynomial roots involve things like the number of roots a polynomial has and whether those roots are real or complex numbers. As you learn more about polynomials and roots, you'll discover other interesting properties and patterns as well!