Aisha just received a $40 paycheck from her new job. She spends some of it buying music online and saves the rest in a bank account. Her savings is given by f(x) = 40 1.25x, where x is the number of songs she downloads at $1.25 per song.
a. Graph the function.

- anonymous

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- anonymous

edit: f(x) = 40 - 1.25x

- anonymous

@jim_thompson5910

- UsukiDoll

put it in y = mx+b form
f(x) also means y
we just need rearranging for the formula

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## More answers

- anonymous

y = -1.25x + 40

- UsukiDoll

yup... now we just graph that... hmm..... not by hand .... with desmos online grapher

- UsukiDoll

##### 1 Attachment

- anonymous

i have to take a pic of it to send it through online, so i gotta do it by hand lol

- UsukiDoll

if we chose x = 0 then y = 40 and that is crazy to graph manually

- UsukiDoll

oh wow XD good luck XD

- anonymous

lol, can u tell me what goes on the x value line and the y value so i can graph?

- UsukiDoll

I think it's torture .... when x = 0 y = 40 so by graph paper you will have to combine sheets

- UsukiDoll

well we can just let x = 0,1,2,3... and then solve for y
same process when x = -1,-2,-3 and then solve for y

- anonymous

i mean, when i graph this manually, the y values will be 0 to 40 and the x values will be..1 2 3 etc?

- UsukiDoll

we can choose our x ... that's why x can be 0,1,2,3. we plug those values into the equation so we can solve for y
when x = 0
y = 1.25(0) +40
y=0+40 = 40
so
(0,40) is a point on the graph

- UsukiDoll

when x = 1
y=1.25(1) +40 = 1.25+ 40 = 41.25
so (1,41.25)

- UsukiDoll

that's torture to draw manually

- anonymous

hmm yea >.< lol i'll see what i can do, thanks!

- UsukiDoll

ugh .. I forgot the negative
ok that didn't make an impact when x = 0
but it does when x = 1
so
y=-1.25+40 = 38.75
(1, 38.75)
that makes better sense.

- UsukiDoll

damn I was half drowsy when I was doing the x = 1 xD

- anonymous

|dw:1438128399818:dw| this is what im kinda confused about

- anonymous

i plot 40 on the y axis, and i gotta go down -1.25 cuz thats the slope, but what numbers do i put on the x axis

- UsukiDoll

if your graphing by 5's... it should be uniformed..
|dw:1438128530205:dw|

- UsukiDoll

wow.. maybe.. let x = 5, 10, 15 into the equation and see what the y-axis becomes.. but I know it's not going to be in 5's

- UsukiDoll

like when x = 5
y = -1.25(5) +40

- anonymous

but even though x represents the number of songs this girl downloads, it should still be like u just drew it? i thought the y axis = the dependent variable, being the money, and the x axis is the independent, being the amount of songs downloaded.

- UsukiDoll

x is the number of songs.. so when x = 5.. that's 5 songs
the more songs bought the less money is left over
so if x = 5 (5 SONGS)
y= -1.25(5) +40
5 songs at $1.25 a piece is (1.25 x 5 = 6.25 or $6.25)
so $6.25 is being deduced from 40 dollars
y=-6.25+40
y=33.75 or $33.75 dollars remaining.

- anonymous

ok i see, thanks

- UsukiDoll

so to find out how many songs can be buy until she goes bankrupt we have to find the x-intercept and that's setting y = 0
0 = -1.25x+40
and solve for x
-40 = -1.25x
dividing -1.25 on both sides gives us 32.
So, she can buy up to 32 songs before going broke

- UsukiDoll

so x is the songs
y is da money
at 0 songs she has her full 40 dollars (0,40) when x = 0 (finding the y-intercept)
at 32 songs she's broke (32,0) when y = 0 (finding the x-intercept)

- anonymous

ty!

- UsukiDoll

I just realized something. you just have to plot the points (0,40) and (32,0). then you can connect the dots.. no manual let x = 1,2,3... what the question was really looking for are the intercepts x*(

- anonymous

yea, i just did it that way ^^

- UsukiDoll

yay :)

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