In this table... is y a function of x?

Question

x | 1 | 2 | 3 | 4 | 5 | 10
y | 5 | 20| 45| 80 |125| 500

the equation is y=5x^2(squared)

is y a function of x?
on the answer key it says it isn't... but i cant seem to understand that. how can that NOT be a function?

Answer 1

It should be a function because one x input value gives only one y output value. Try the vertical-line test. But the function does not have an inverse though.

Answer 2

If you plug each value given for x into your equation, you should get every y value that is in the chart.

I can see that y is a function of x.

I will do two only. You can do the rest.

y = 5(x^2)

If x = 1, what is y?

y = 5(1)^2

y = 5

Next:

If x = 2, what is y?

y = 5(2)^2

y = 5 times 4

y = 20

You can do the rest but like I said before, it appears that y is a function of x based on the information given in the chart.

WHY????

Well, because when we plug each x value given into the equation, we get each y value that is also given in the chart.

Guido

Answer 3

The answer key is wrong. You have provided an equation which reliably generates a value for y, and only one value of y, for every value of x. That is pretty much the definition of a function.

Answer 4

I agree with you.