Exponential Functions
Exponential Growth
Exponential Decay
Created by:David W. Cummins
A population of 130,000 increases by 1% each year.
Initial value? a = 130000
Growth or decay? Growth!b will be greater than 1.
b = 100% + 1% = 101% = 1.01Growth factor?
Exponential Equation: y = abx
y = (130000)(1.01)x
Find population size in 7 years!
x = 7y = (130000)(1.01)7
y = 139377.5958
Or approximately 139,000
y = (130000)(1.01)x
A population of 3,000,000 decreases by 1.5% each year.
Initial value? a = 3000000Growth or decay? Decay!
b will between 0 and 1.
b = 100% - 1.5% = 98.5% = .985Decay factor?
Exponential Equation: y = abx
y = (3000000)(.985)x
Find population size in 5 years!x = 5
y = (3000000)(.985)5
y = 2,781,649.507
Or approximately 2.78 million
y = (3000000)(.985)x
An item purchased for $900 has a 20% loss in value each year.
Initial value? a = 900
Growth or decay?Decay!b will between 0 and 1.
b = 100% - 20% = 80% = .80Decay factor?
Exponential Equation: y = abx
y = (900)(.80)x
Find value in 6 years!x = 6
y = (900)(.80)6
y = 235.9296
Or $235.93
y = (900)(.80)x
An investment of $3,000 earns 4% interest compounded annually.
Initial value?a = 3000Growth or decay? Growth!
b will be greater than 1.
b = 100% + 4% = 104% = 1.04Growth factor?
Exponential Equation: y = abx
y = (3000)(1.04)x
Find population size in 8 years!x = 8
y = (3000)(1.04)8
y = 4105.707151
Or $4105.71
y = (3000)(1.04)x
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