identify vertical intercept and slope

[santaclaus]

I'm supposed to identify vertical intercept and slope and explain meanings in practical terms. I understand what vertical intercept is , and I know how to get slope, but I am confused when it's in a word problem like below:

1. The population of a town can be represented by the formula P(t) = 54.25 - 2/7t, where P(t) represents the population, in thousands and t represents the time in years, since 1970. (Does this mean that P(t) is y and 2/7 is my slope?)

2. The profit, in dollars of selling n items is given by P(n)=0.98n-3000.
(does this mean that .98 is the slope, -3000 is y-intercept? but what is vertical intercept -- do I have to put it into another equation - or solve by putting in values for n?)

3. A phone company charges according to the formula C(n)=29.99 +0.05n, where n is the number of minutes, and C(n) is the monthly phone charge, in dollars

still don't understand vertical intercept -- I think the .05 is the slope though

[stapel_eliz]

I understand what vertical intercept is...

Um... I don't. I've heard of x-intercepts and y-intercepts, but not "vertical" intercepts. How does your book define this?

1. The population of a town can be represented by the formula P(t) = 54.25 - 2/7t, where P(t) represents the population, in thousands and t represents the time in years, since 1970.
(Does this mean that P(t) is y and 2/7 is my slope?)

Yes.

2. The profit, in dollars of selling n items is given by P(n)=0.98n-3000.
(does this mean that .98 is the slope, -3000 is y-intercept?

Yes.

...but what is vertical intercept -- do I have to put it into another equation - or solve by putting in values for n?)

Dunno. See my question above, in response to exercise (1).

3. A phone company charges according to the formula C(n)=29.99 +0.05n, where n is the number of minutes, and C(n) is the monthly phone charge, in dollars
still don't understand vertical intercept -- I think the .05 is the slope though

You're right about the slope.