We are asked to decide if the expression:
x^2 + y^2 = 1 represents a function.
We recall that in order to have a function, we need for a given value of x to have a SINGLE value of y associated with it.
So in this case, when x is 0 for example, we have the following:
0^2 + y^2 = 1
then y^2 = 1
and we realize that there are TWO values of y whose square form gives 1 (one is 1 and the other -1) Therefore, this relationship is NOT a function, since for example when x = 0 there are TWO values of y to which that x is associated (y = 1 and y = -1).
So please select that this is NOT a function for your answer.
Answer: 286 minutes
Step-by-step explanation:
x : # of months that has gone by
0.24x : cost of the 24 cent plan after "x" minutes
39.95 + 0.10x : cost of the 10 cent plan after "x" minutes
1. 39.95 + 0.10x > 0.24x
2. 39.95 > 0.24x - 0.10x
3. 39.95 > 0.14x
4. 285.36 > x
x must be AT LEAST 286 minutes for plan #2 (39.95 + 0.10x) to be a better deal
