<span>1.
"The spending limit on John’s credit card is given by the function f(x)=15,000+1.5x"
means that if the monthly income of John is $ 5,000 ,he can spend at most
f(5,000)=15,000+1.5*5,000=15,000+ 7,500=22, 500 (dollars)
Or for example
if Johns monthly income is $8,000, then he can spend at most
</span>f(8,000)=15,000+1.5*8,000=15,000+ 12,000=27,000 (dollars)<span>
2.
Now, assume that the maximum amount that John can spend is y.
Then, y=15,000+1.5x
we can express x, the monthly income, in terms of y by isolating x:
</span>y=15,000+1.5x
<span>
1.5x = y-15,000
</span>
<span>
thus, in functional notation, x, the monthly income, is a function , say g, of variable y, the max amount:
</span>
since we generally use the letter x for the variable of a function, we write g again as:
<span>
for example :
</span>
<span>
tells us that if the maximum amount that John can spend is 50,000 $, then his monthly income is 23,333 $.
3.
If John's limit is $60,000, his monthly income is
</span>
<span>
dollars.
Answer: $ 30,000
Remark: g is called the inverse function of f, since it undoes what f does.
instead of g(x), we could use the notation </span>
<span>
</span>
"The spending limit on John’s credit card is given by the function f(x)=15,000+1.5x"
means that if the monthly income of John is $ 5,000 ,he can spend at most
f(5,000)=15,000+1.5*5,000=15,000+ 7,500=22, 500 (dollars)
Or for example
if Johns monthly income is $8,000, then he can spend at most
</span>f(8,000)=15,000+1.5*8,000=15,000+ 12,000=27,000 (dollars)<span>
2.
Now, assume that the maximum amount that John can spend is y.
Then, y=15,000+1.5x
we can express x, the monthly income, in terms of y by isolating x:
</span>y=15,000+1.5x
<span>
1.5x = y-15,000
</span>
<span>
thus, in functional notation, x, the monthly income, is a function , say g, of variable y, the max amount:
</span>
since we generally use the letter x for the variable of a function, we write g again as:
<span>
for example :
</span>
<span>
tells us that if the maximum amount that John can spend is 50,000 $, then his monthly income is 23,333 $.
3.
If John's limit is $60,000, his monthly income is
</span>
dollars.
Answer: $ 30,000
Remark: g is called the inverse function of f, since it undoes what f does.
instead of g(x), we could use the notation </span>
</span>
