2.2 Power Function w/ modeling

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2.2 Power Function w/ modeling. 2.3 Polynomials of higher degree with modeling. Power function. A power function is any function that can be written in the form: f(x) = kx a , where k and a ≠ 0 Monomial functions: f(x) = k or f(x) = kx n Cubing function: f(x) = x 3

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2.2 Power Function w/ modeling

2.3 Polynomials of higher degree with modeling

Power function
• A power function is any function that can be written in the form:

f(x) = kxa, where k and a ≠ 0

• Monomial functions: f(x) = k or f(x) = kxn
• Cubing function: f(x) = x3
• Square root function: f(x) = x
• Higher degree: (standard form)

p(x) = anxn + an-1xn-1 + an-2xn-2 +… + a1x + a0

Analyzing Power functions
• To do you will find the following:

domain

range

continuous/discontinuous

increasing/decreasing intervals

even (symmetric over y-axis)/odd function (symmetric over origin)

boundedness

local extrema (max/min)

asymptotes (both VA and HA)

end behavior (as it approaches both -∞ & ∞

Example: analyze f(x) = 2x4
• Power: 4, constant: 2
• Domain: (-∞,∞)
• Range: [0, ∞)
• Continuous
• Increasing: [0,∞), decreasing: (-∞, 0]
• Even: symmetric w/ respect to y-axis
• Bounded below
• Local minimum: (0, 0)
• Asymptotes: none
• End behavior: lim 2x4 = ∞, lim 2x4 = ∞

x -∞ x ∞

(in other words, on the left the graph goes up, on the right the graph goes up)

Try one: f(x) = 5x3

Investigating end behavior
• When determining end behavior you need to determine if the graph is going to -∞ (down) or ∞ (up) as x -∞ & as x ∞
• Example: graph each function in the window [-5, 5] by [-15, 15] . Describe the end behavior using lim f(x) & lim f(x)

x -∞ x ∞

• f(x)=x3+2x2-5x-6: -∞,∞
• Do exploration
Finding 0’s
• Find the 0’s of f(x) = 3x3 – x2 -2x
• Algebraically: factor

3x3 – x2 -2x = 0

x(3x2 – x -2) = 0

x(3x + 2)(x - 1) = 0

x = 0, 3x + 2 = 0, x – 1= 0

x = 0, x = -2/3, x = 1

• Graphically: graph & find the 0’s (2nd trace #2)
Zeros of Polynomial function
• Multiplicity of a Zero

If f is a polynomial function and (x-c)m is a factor of f but (x – c)m+1 is not, then c is a zero of multiplicity m of f.

• Zero of Odd and Even Multiplicity:

If a poly. funct. f has a real 0 c of odd multiplicity, then the graph of f crosses the x-axis at (c, 0) & the value of f changes sign at x=c

if a poly. funct. f has a real 0 c of even multiplicity, then the graph doesn’t cross the x-axis at (c, 0) & the value of f doesn’t change sign at x=0

Multiplicity
• State the degree, list the 0’s, state the multiplicity of each 0 and what the graph does at each corresponding 0. then sketch the graph by hand (look at exponents: if 1 then crosses, if odd then wiggles, if even then tangent)
• Examples: 1)f(x) = x2 + 2x – 8

degree: 2, 0’s: 2, -4, graph: crosses at x=-4 & x= 2

2) f(x) = (x + 2)3(x-1)(x-3)2

Now finish paper

Writing the functions given 0’s
• 0, -2, 5

1) rewrite w/ a variable & opposite sign:

x(x + 2)(x – 5)

2) simplify

x(x2 -3x + -10)

x3 – 3x2 – 10x

Try one: -6, -4, 5

Homework:
• p. 182 #1-10, 27-30
• p. 193-194 #2-6 even, 25-28 all, 34-38 even, 39-42 all, 49-52 all, 53, 54