The credit remaining on a phone card (in dollars) is a linear function of the total calling time made with the card (in minutes). the remaining credit after 39 minutes of calls is $25.32, and the remaining credit after 57 minutes of calls is $23.16. what is the remaining credit after 60 minutes of calls?

One way to write a linear equation is the formula y = mx + b where m is the slope of the function and b is the y-intercept. For this reason, it is known as slope-intercept form.

The slope os calculated via the formula . Lets calculate the slope of the equation first.

So the slope is -0.12. This means for every minute of time used, $0.12 of credit is used. Next, lets plug in the value for m, and the values of an x and y point to find b.

y = 0.12x + b

23.16 = -0.12(57) + b

23.16 = -6.84 + b

30 = b

So, our final equation is y = -0.12x + 30.

Finally, we can use this equation to find the answer to the last part by plugging the value into x.

y = -0.12(60) + 30

y = -7.2 + 30

y = 22.8

So when 60 minutes have been used, there will be $22.80 worth of credit left.

hello from mrbilldoesmath!

answer:

a(n) - a(n-1) -3

discussion:

this ones a bit interesting. given a(n) = 5 - 3n consider this:

a(n-1) = 5 - 3(n-1)

          = (5 - 3n) + 3             => but a(n) = 5 - 3n, the first term

          = a(n)   + 3                 => subtract 3 from both sides

a(n-1) -3 = a(n)  

or

a(n) - a(n-1) -3

you,

mrb

homozygous. one is homozygous, while two is heterozygous.