Check it out!

1. Check it out! 1.3.2: Creating and Graphing Exponential Equations

2. Read the scenario and answer the questions that follow. One form of the element beryllium, beryllium-11, has a half-life of about 14 seconds and decays to the element boron. A chemist starts out with 128 grams of beryllium-11. She monitors the element for 70 seconds. What is the equation that models the amount of beryllium-11 over time? How many grams of beryllium-11 does the chemist have left after 70 seconds? 1.3.2: Creating and Graphing Exponential Equations

3. What is the equation that models the amount of beryllium-11 over time? y = abx, where y is the final value, a is the initial value, b is the rate of growth or decay, and x is the time. y = unknown a = 128 grams b = 0.5 Time = 70 seconds, but this needs to be converted to time periods before substituting the value for x. 1.3.2: Creating and Graphing Exponential Equations

4. Convert 70 seconds into 14-second time periods. 1 time period = 14 seconds x = 5 Substitute all the variables into the equation. y= abx y = 128(0.5)5 1.3.2: Creating and Graphing Exponential Equations

5. How many grams of beryllium-11 does the chemist have left after 70 seconds? Apply the order of operations to the equation from the end of problem 1. y = 128(0.5)5 y = 4 grams 1.3.2: Creating and Graphing Exponential Equations