Dianne knows a phone call a friend for the first 3 minutes costs 25 cents and 10 cents for each additional minute
1 answer:
Question:
Diane knows a phone call to a friend costs .25 for the first three minutes and .10 for each additional minute. Let y be the cost of a call that lasts x minutes. Write the slope and an equation relating x and y.
Answer:
Slope = 0.10 or
Equation relating x and y is y = 0.10x- 0.05
Step-by-step explanation:
Given:
Cost for first three minutes = 0.25 cents
Cost for each additional minute = 0.10 cents
To Find:
The slope and an equation relating x and y = ?
Solution:
Let y be the cost of a call that lasts x minutes
Then,
y = 0.25 + 0.10(x-3)
y = 0.25 + 0.10x- 0.30
y = 0.10x- 0.05-------------------(1)
In the equation
y = mx +b------------------------------(2)
m is the slope
Comparing eq(1) and(2)]
m =0.10 or
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Answer:
No because it contains points (3,4) and (3,-4). You cannot have a x assigned to more than one y-value if you want it to be a function.
Step-by-step explanation:
A function has one output per input.
If we are trying to determine if the given is a function of x, then x is the input.
However I can get two outputs from plugging in x=3.
Subtract 9 on both sides:
Take the square root of both sides:
.
So input x=3 yields y=4 and y=-4.
Since this input has more than one output then the given is not a function of x.
----Also!
If you graph the equation, it is a circle with radius 5 and center (0,0). So I could I plug in any number for x between -5 and 5 excluding -5 and 5 which would yield only one output each. Since plugging in either one gives:
Subtract 25 on both sides:
Simplify:
There is only one value y such that when you square it gives you 0. That is 0.
x=5 only gives y=0 and x=-5 only gives y=0.
There is no circle, unless it is a circle with radius 0 which means it really wouldn't be a circle, that is a function.