Notes 7.7 algN.notebook
January 11, 2016
Notes Section 7.7 ‐ TLW model exponential growth and decay
growth: b = (1 + %)
decay: b = (1 - %)
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Tell whether each equation or graph represents exponential growth, exponential decay, or neither. 3.
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Notes 7.7 algN.notebook
January 11, 2016
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Suppose a park's population of deer in 1980 was 230 and it grows about 2.5% each year, what will the approximate population be in 1988? What is the growth factor? What is the initial amount?
230(1+.025)8 = 281 deer
When a bank pays interest on both the principal and the interest an account has already earned, the bank is paying compound interest. Compound interest is an example of exponential growth. You can use the formula below to find the balance in an account that earns compound interest.
12. Suppose that when your friend was born, your friends's parents deposited $2000 in an account paying 4.5% interest compounded quarterly. What will the account balance be after 18 years?
13. Find the balance in an account after $3500 is deposited in the bank earning a 3.6% interest compounded semiannually for 2 years.
Notes 7.7 algN.notebook
January 11, 2016
14.
The atmospheric pressure at 5000m is kilopascals.
15. A business purchases a computer system for $2000. The tax code allows them to take off a portion of that purchase for each year the computer system is used. If the value of the system is depreciated at a rate of 15% per year, the function that models the current value of the system is f(x) = 2000(1-.15)x
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How much is the computer worth after 4 years? 2000(1-.15) =$1044.01
Do you understand?
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16. What is the growth factor in the equation 15
17. What is the initial amount in the function 18. What is the decay factor in the function
0.2
19. A population of fish in a lake decreases 6% annually, what is the decay factor?
1-.06=.94
20. How can you tell if an exponential function models growth or decay?
if the base is below 1 it is decay and
over 1 is growth