Aim # 7.4: How do we solve exponential equations?

Part 1: Solving exponential equations using “like bases”

One way to solve exponential equations is to use “like bases” because when we have like bases, then

So, the steps are: rewrite as like bases Set _______________________________________ equal to each

other Solve for the variable. Ex. A: 92x = 27x – 1

More Practice

1007x + 1 = 10003x – 2

813 –x = 5x-6

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Part 2: Solving exponential functions that can’t have “like bases”

What option do we have if they can’t be rewritten using like bases? Well, we have to use our knowledge of inverse properties to solve

the equations. Steps: 1st: Use SADMEP to get the base by itself on one side of

the equal sign 2nd: Depending on the base, add a log or natural log to the

problem. **REMEMBER – whatever you do or add to one side, you have to do

or add to the other!!!! 3rd: Use log properties and SADMEP again (if necessary) to

solve for the variable.

EXAMPLES:

a. 4x = 11 b. 79x = 15 c. 4e-

0.3x – 7 = 13

Interest and Depreciation

Interest is the money earned on an investment. This could be a bank account, certificate of deposit, stocks, bonds, loan to someone, etc. Depreciation is the money lost over time on something purchased. The best example of this is, is a car.

 Interest: Interest can be compounded (calculated) once a year, twice a year, three times a year, etc, up to continuously. We will use the compound interest formula:

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If we compound: we calculate interest (per year): Quarterly 4 times Monthly 12 times Bi-monthly 24 times Weekly 52 times Daily 365 times EX: You deposit $4000 in an account that pays 2.92% annual

interest. Find the balance after 1 year if the interest is compounded

a) quarterly, b) daily, C) How long will it take to earn $8350?

Depreciation:The equation for depreciation is: y = a(1 – r)n

  So, let’s use it.EX: A new snowmobile costs $4200. The value of the snowmobile decreases by 10% each year. Find the value of the snowmobile after: a) 1 year, b) 4 years, c) How many years will it take for the value to be $800?         

EX: You invest $500 in the stock of a company. The value of the stock decreases 2% each year. Find the value of the stock after a) 1 year, b) 3 years, c) How long will it take for the value to reach $175? 

More Practice:

Summary: Answer in complete sentences.

1. What is the difference between interest and depreciation?

2. Which formula do you use to solve interest and depreciation?

3. What are some key words in the word problem that clue you in on an interest problem?

B. depreciation problem?