Algebra 2 Exponential and Logarithmic Functions Lesson 8-5

Algebra 2 Solve 5 2x = x = 16 log 5 2x = log 16Take the common logarithm of each side. 2x log 5 = log 16Use the power property of logarithms. x = Divide each side by 2 log 5. log 16 2 log Use a calculator. Check: 5 2x (0.8614) 16 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples

Algebra 2

Lesson 8-5 Exponential and Logarithmic Equations Additional Examples Solve 4 3x = 1100 by graphing. The solution is x Graph the equations y = 4 3x and y = Find the point of intersection.

Algebra 2 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples Use a calculator log 3 log xMultiply each side by log log x Use a calculator log xSimplify. x Write in exponential form. The expression log 6 12 is approximately equal to , or log (continued)

Algebra 2 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples Solve 5 2x = 120 using tables. Enter y 1 = 5 2x – 120. Use tabular zoom-in to find the sign change, as shown at the right. The solution is x 

Algebra 2 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples The population of trout in a certain stretch of the Platte River is shown for five consecutive years in the table, where 0 represents the year If the decay rate remains constant, in the beginning of which year might at most 100 trout remain in this stretch of river? Time t01234 Pop. P(t) Step 1: Enter the data into your calculator. Step 2: Use the Exp Reg feature to find the exponential function that fits the data.

Algebra 2 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples Step 3: Graph the function and the line y = 100. Step 4: Find the point of intersection. The solution is x 18, so there may be only 100 trout remaining in the beginning of the year (continued)

Algebra 2

Lesson 8-5 Exponential and Logarithmic Equations Additional Examples Use the Change of Base Formula to evaluate log Then convert log 6 12 to a logarithm in base 3. log 6 12 = Use the Change of Base Formula. log 12 log Use a calculator log 6 12 = log 3 xWrite an equation log 3 xSubstitute log 6 12 = = x Re-Write in Exponential Form and Solve! x 4.59

Algebra 2 log = Use the Change of Base Formula. log 400 log Use a calculator log = log 8 xWrite an equation log 8 xSubstitute log = = x Re-Write in Exponential Form and Solve! x

Algebra 2 Solve log (2x – 2) = 4. log (2x – 2) = 4 2x – 2 = 10 4 Write in exponential form. 2x – 2 = x = 5001Solve for x. log 10 4 = 4 log 10,000 4 log ( – 2) 4 Check:log (2x – 2) 4 Lesson 8-5 Exponential and Logarithmic Equations Additional Examples

Algebra x = Write in exponential form x = 0.1 x = (6.9)/2Solve for x. x = 3.45

Algebra 2 Solve 3 log x – log 2 = 5. 3 log x – log 2 = 5 x32x32 Log ( ) = 5Write as a single logarithm. x32x32 = 10 5 Write in exponential form. x 3 = 2(100,000)Multiply each side by 2. x = , or about The solution is , or about Lesson 8-5 Exponential and Logarithmic Equations Additional Examples

Algebra 2 6 3x Log ( ) = -2Write as a single logarithm. 2x2x = =Write in exponential form. x = 200Cross Multiply The solution is B, x =

Algebra 2