Writing and interpreting functions

The amount Lea can earn at her job is shown:
She earns $7 per hour for the first 40 hours. 
She earns 1.5 times the hourly wage for every hour over 40 hours. 
Which piecewise-defined function best represents Lea’s weekly pay, P(h), where h represents the hours worked?

• P(h)= 7h,   0≤h≤40
  P(h)=10.5h−140,   h>40
• P(h)= 7h,   0<h<40
  P(h)= 10.5h−140,     h>40
• P(h)= 7h,     0≤h≤40
  P(h)= 10.5h+140,     h≥40
• P(h)=   7h, 0<h<40  P(h)= 10.5h+140,   h≥40

A function that is defined by different sets of input values is said to be a piece-wise function.

• TRUE

• FALSE

Write the second line of the piecewise function given the second sentence.

After 500 text messages, it costs $0.10 per text you send.

x: number of text messages

f(x): cost of cell phone plan

• $500\ +\ 0.10\left(x-75\right)\ if\ x\ge500$

• $500\ +\ 0.10\left(x-75\right)\ if\ x>75$

• $75\ +\ 0.10\left(x-500\right)\ if\ x>500$

• $75+0.10\left(x-500\right)\ if\ x\ge500$

Evaluate f(2.7)

• 2

• 3

• 2.5

• 2.7

The following graph shows the price of a certain computer chip over time. Which context below correctly matches the graph?

• On January 1, 1998, the price of a certain computer chip was $145. That price was the same through to the next 3 years. Beginning January 1, 2001 and for every exact block of two years thereafter, the price of the chip decreased by $89.

• On January 1, 1998, the price of a certain computer chip was $145. That price was the same through to the next 3 years. Beginning January 1, 2001 and for every exact block of two years thereafter, the price of the chip decreased by $14.

• On January 1, 1998, the price of a certain computer chip was $89. That price was the same through to the next 3 years. Beginning January 1, 2001 and for every exact block of two years thereafter, the price of the chip increased by $14.

• On January 1, 1998, the price of a certain computer chip was $145. That price was the same through to the next 2 years. Beginning January 1, 2000 and for every exact block of three years thereafter, the price of the chip decreased by $14.

Evaluate f(0.5).

• 4

• 6

• 0

• 2

The range is {4, 8, 12, 16, 20, 24}

• Trick
• True

Evaluate t(0)

• 0

• 19

• 9

• -19

(a) write a piece wise

(b) then determine what the charge will be for using 150 terms in a month

• A.) {15.95 + .27x; x ≤ 50

  {32.45+ .33( x-50); x > 50

  
  

  B.) $50.60

• A.) {15.95 + .33x; x ≤ 50

  {32.45+ .27( x-50); x > 50

  
  

  B.) $54.95

• A.) {15.95 + .33x

  {32.45+ .27(x-50)

  
  

  B.) $45.54

• A.) { 15.95 + .33x; x ≤ 15.95

  { 32.45+ .27( x-50); x > 15.95

  
  

  B.) $54.54