Writing exponential growth or decay functions

Write the exponential function for :

 A population of beetles that starts at 50 increases by 65% each year.

• $f\left(x\right)\ =\ 50\ \left(.65\right)^x$

• $f\left(x\right)=\ 50\left(1.65\right)^x$

• $f\left(x\right)\ =\ 65\left(.50\right)^x$

• $f\left(x\right)=\ 50\left(.35\right)^x$

Write the exponential function for :

  Your heart rate reaches 58 bpm and then increases by 20% each minute.

•  $f\left(x\right)\ =\ 58\ \left(.20\right)^x$ 

•  $f\left(x\right)=\ 58\left(1.20\right)^x$ 

•  $f\left(x\right)\ =\ 20\left(.58\right)^x$ 

•  $f\left(x\right)=\ 58\left(.80\right)^x$ 

Write the exponential function for :


 An account with $25,000 decreases in value 9% each year.

•  $f\left(x\right)\ =\ 25,000\left(.90\right)^x$ 

•  $f\left(x\right)=25,\ 000\left(0.09\right)^x$ 

•  $f\left(x\right)\ =\ 25,000\left(.91\right)^x$ 

•  $f\left(x\right)=\ 25,000\left(1.09\right)^x$ 

Write the exponential function for :

 A new car you bought for $48,000 decreases in value 10% each year.

•  $f\left(x\right)\ =48,000\left(.90\right)^x$ 

•  $f\left(x\right)=48,000\left(0.10\right)^x$ 

•  $f\left(x\right)\ =48,000\left(1.10\right)^x$ 

•  $f\left(x\right)=48,000\left(1.01\right)^x$ 

Alex invests in a savings account that pays 3.50% interest increases quarterly. What is the decay/growth factor?

•  $100\ \%\ +\ 3.50\ \%\$  

•  $100\%\ -3.50\%$  

•  $100\ \%\ \cdot\ 3.50\ \%$  

•  $100\%\ \div3.50\%$  

Alex invests in a savings account that increases by  3.50% quarterly. What is the growth/decay factor?

• 1350%= 13.50 

• 96.5% = .965

• 103.50% = 1.035

• 10.35%= .1035

To write the exponential function for :

 A population of beetles that starts at 50 increases by 65% each year.

What is the 1st step?

• Add  $100+\ 65\%$  

• Subtract  $100-65\%$  

• change the  $65\ \%$  to a decimal by moving it two units to the left
  

• change the  $65\ \%$  to a decimal by moving it two units to the righy
  

In an exponential function, to have an increase of 15% you have do the following: 

(select 2)

•  $Add\ \ \ \ \ \ 100\%\ +\ 15\%\ \ \$  

• Change 115% to a decimal which is 1.15

•  $Subtract\ \ \ \ 100\%\ -15\%$  

• Change 85% to a decimal which is 0.85

To write the exponential function for :


An account with $25,000 decreases in value 9% each year.

What is the 1st step?

• Add  $100+\ 9\%$  

• Subtract  $100-9\%$  

• change the  $9\ \%$  to a decimal by moving it two units to the left
  

• change the  $9\%$  to a decimal by moving it two units to the right
  

In an exponential function, to have an decrease of 9% you have do the following: 

(select 2)

•  $Add\ \ \ \ \ \ 100\%\ +\ 9\%\ \ \$  

• Change 109% to a decimal which is 1.09

•  $Subtract\ \ \ \ 100\%\ -9\%$  

• Change 91% to a decimal which is 0.91