M 112 Short Course in Calculus
description
Transcript of M 112 Short Course in Calculus
M 112 Short Course in Calculus
Chapter 1 – Functions and ChangeSections 1.5 Exponential FunctionsV. J. Motto
1.4 Exponential Functions
An exponential function is a function of the form
Where a ≠ 0, b > 0, and b ≠ 1. The exponent must be a variable.
04/24/23 2
xy = a*b
Illustration 1
04/24/23 3
Illustration 2: Different b’s, b > 0
04/24/23 4
What conclusions can we make looking at these graphs?Use your calculator to sketch these graphs!
Illustration 3: Different b’s, 0 < b <1
04/24/23 5
Graph these on your calculator. What can we conclude? Are there other ways to write these equations?
Comments on y = bx
All exponential graphs Go through the point (0, 1)Go through the point (1, b)Are asymptotic to x-axis.
The graph f(x) = b-x =
04/24/23 6
1 x
b
Illustration 4: (page 39)
Population of Nevada 2000-2006 Dividing each year’s population by the previous year’s population gives us
We find a common ratio!
04/24/23 7
Illustration 4 (continued)
These functions are called exponential growth functions. As t increases P rapidly increasing.
04/24/23 8
Thus, the modeling equation is P(t) = 2.020(1.036)t
Illustration 5: Drugs in the Body
Suppose Q = f(t), where Q is the quantity of ampicillin, in mg, in the bloodstream at time t hours since the drug was given. At t = 0, we have Q = 250. Since the quantity remaining at the end of each hour is 60% of the quantity remaining the hour before we have
04/24/23 9
Illustration 5: (continued)
You should observe that the values are decreasing! The function Q = f(t) = 250(0.6)t
Is an exponential decay function. As t increases, the function values get arbitrarily close to zero.
04/24/23 10
Comments
The largest possible domain for the exponential function is all real numbers, provided a >0.
04/24/23 11
Linear vs Exponential
Linear function has a constant rate of change
An exponential function has a constant percent, or relative, rate of change.
04/24/23 12
Example 1: (page 41)
The amount of adrenaline in the body can change rapidly. Suppose the initial amount is 25 mg. Find a formula for A, the amount in mg, at time t minutes later if A is
a) Increasing by 0.4 mg per minuteb) Decreasing by 0.4 mg per minutec) Increasing by 3% per minuted) Decreasing by 3% per minute
04/24/23 13
Example 1: (continued)
Solutiona)A = 25 + 0.4 t - linear increaseb)A = 25 – 0.4t - linear decreasec)A = 25(1.03)t - exponential growthd)A = 25(0.97)t - exponential decay
04/24/23 14
Example 3: (page 42)
Which of the following table sof values could correspond to an exponential function or linear function? Find the function.
04/24/23 15
Example 3: (continued)
a) f(x) = 15(1.5)x, (common ratio)b) g is not linear and g is not exponentialc) h(x) = 5.3 + 1.2x
04/24/23 16
Research Homework
Search the internet (or mathematics books you own) and find a demonstration that discovers the value of e.
04/24/23 17