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Polynomial functions

Degree, end behaviour, zeros, turning points, and what the graph must look like.

A polynomial of degree n has at most n real zeros and at most n − 1 turning points, and its ends point where the leading term sends them. Factoring finds the zeros; the derivative finds the turning points. Type a polynomial as y = … to see all of it at once.

Kugwira ntchito chitsanzo: y = x^3 - 3x

Algebra · Functions

Graph and analyse x^3 - 3x

y = x^{3} - 3 x

Gawo ndi Gawo

  1. x^{3} - 3 x

    An expression in x. Here is what it does.

  2. x \left(x^{2} - 3\right)

    Simplified form.

  3. x = 0, x = - \sqrt{3}, x = \sqrt{3}

    Real zeros (where the graph crosses the axis).

  4. \frac{d}{dx} = 3 x^{2} - 3

    Derivative (slope).

Kusonyeza yankho
x \left(x^{2} - 3\right)

Symbols used here

\sqrt{x},\ \sqrt[n]{x}
square root, n-th root
The non-negative number whose square (n-th power) is x.
f'(x),\ \frac{dy}{dx}
derivative
Instantaneous rate of change; slope of the graph.
\leq,\ \geq
less/greater than or equal
Inequalities that allow equality; < and > exclude it.
|x|
absolute value / modulus
Distance from zero: |−3| = 3. For a complex number, distance from the origin.
\binom{n}{k}
binomial coefficient, "n choose k"
Number of k-element subsets of n things: n!/(k!(n−k)!).
\pi
pi
Ratio of a circle's circumference to its diameter, 3.14159…
e
Euler's number
2.71828…, the base whose exponential is its own derivative.
i
imaginary unit
i² = −1.
\theta
theta
The usual name for an angle.
\log_b x,\ \ln x
logarithm, natural log
The exponent b must be raised to for x; ln uses base e.
\mathbf{v},\ \vec{v}
vector
A quantity with magnitude and direction; a column of numbers.

How to: Polynomial functions

  1. An expression in x. Here is what it does.
  2. Simplified form.
  3. Real zeros (where the graph crosses the axis).
  4. Derivative (slope).

Questions people ask

What is a function, really?

A rule that assigns exactly one output to each input. The vertical-line test on a graph is the same idea: no input may have two outputs.

Why do we need complex numbers?

Because x² + 1 = 0 has no real solution, and allowing one new number i with i² = −1 makes every polynomial equation solvable. They then turn out to describe rotation, waves and alternating current more naturally than real numbers do.

Sankhani wanu

Zambiri pa Precalculus

Complex numbersRational functionsSequences and seriesThe binomial theoremConic sectionsVectorsExponential and logarithmic functionsPolynomial division and the remainder theoremParametric equations and polar coordinates