2. Functions and Sequences

Calculus 1



Weiqi Zhou

Powers

  • with





Read and Think

now that you know what for means,
how do we define for ?

Polynomials



  • is the order of the polynomial
    are called coefficients

  • is a root of if

  • a polynomial of order has roots (counting multiplicities) in

Linear Case

  • y=kx+b

  • is the slope and determines the direction

  • is the intercept (on the -axis)

Linear Case

  • is also the tangent of the angle between the line and the x-axis

  • if the line crosses and with , then


Exercises

I will write some pairs of points on the board
for each pair, you shall find the expression of the line that crosses it

Quadratic Case



  • determines to which side the graph is opening

  • it may have 0,1 or 2 real roots

Quadratic Case

  • roots at

  • attains a maximum/minimum at


Exercises

I will write some quadratic polynomials on the board
you shall plot them, find their real roots (if any) and maximum/minimum points

Familiarize Yourself with

Exponentials and Logarithms

  • if , then
    is written as




Exponentials

  • defined on entire

  • omits all non-positive values (in particular, NEVER 0)

  • monotonically increasing, and increases drastically fast (faster than any polynomials)

Logarithms

  • defined only for positive

  • assumes all values in (in particular, has one root at )

  • monotonically increasing, but increases pathetically slow (slower than any polynomials)

Sequences

  • a sequence is a function with domain in

  • usually we take subsripts in or and write the sequence out by enumeration:

  • it can be defined explicitly, e.g.,
    or recursively, e.g.,

Arithemetic Progressions

  • a sequence of form (i.e., ) is called an arithemetic progression

  • is the common difference

Geometric Sequences

  • a sequence of form (i.e., ) is called a geometric sequence

  • is the common ratio

Exercises

I will write some finite sequences on the board
you shall compute the sum of each sequence

Summary

  • powers and arithemetics on exponents

  • polynomials

  • exponentials and logarithms

  • sequences