Help on a math question??

[neymar]

A local cell phone provider offers a basic cell phone plan for a monthly fee of $20. This plan includes unlimited texting and a generous data package but charges $0.10 per minute for the first 400 minutes used in a month. The plan then charges $0.50 per minute for additional minutes used over 400.

a) Write a piecewise-defined function, f(x), that models monthly cost in dollars in terms of minutes used, x. Express each of the two linear equations in slope-intercept form (y = mx+b).

b) Sketch this function. LABEL AND TITLE THE GRAPH APPROPRIATELY.

i got the equation to 20+.1x, for 0<=x<=400 but idk how to include the last part of the information in this (the part about it charging 0.50 after 400 mins)

and i'm not quite sure how to find points for the graph! please help!

thanks!

 

[DrPhil]

A local cell phone provider offers a basic cell phone plan for a monthly fee of $20. This plan includes unlimited texting and a generous data package but charges $0.10 per minute for the first 400 minutes used in a month. The plan then charges $0.50 per minute for additional minutes used over 400.

a) Write a piecewise-defined function, f(x), that models monthly cost in dollars in terms of minutes used, x. Express each of the two linear equations in slope-intercept form (y = mx+b).

b) Sketch this function. LABEL AND TITLE THE GRAPH APPROPRIATELY.

i got the equation to 20+.1x, for 0<=x<=400 but idk how to include the last part of the information in this (the part about it charging 0.50 after 400 mins)

and i'm not quite sure how to find points for the graph! please help!

thanks!

Calculate what the cost is for 400 minutes, then add 0.50*(x - 400) to get the 2nd piece of the function.

Your graph will be two straight lines. You can draw the first one by connecting the points for x=0 and for x=400. For the upper partyou can calculate any point above x=400, or use slope = 0.5.