Question

The graph shows the equation x2 + y2 = 5. Use the slider for a to move the vertical line on the graph. Based on the vertical

line test, is this equation a function? Why or why not?

Answer 1

No. The vertical line touches the graph at more than one point at once.

Explanation:

I just did it

Answer 2

Answer: This equation is not a function.

Explanation:

Ok, a function is something like a "machine".

It takes an input value, x, and transforms it into an output value, y.

Such that for every input x, the function can transform it into only one value of y.

for example, if we have a "function" f(x)

such that f(2) = 3 and f(2) = 4

(for the same input, x = 2, we have two different outputs)

Then this is not a function.

Now, the given equation is:

x^2 + y^2 = 5

This is actually the equation for a circle, centered at the point (0, 0) and with a radius equal to √5.

Then, if we want to transform it into y(x), we can see a problem

If x = 0, we have:

0^2 + y^2 = 5

y^2 = 5

then we have two possible values for y:

y = +√5

y = -√5

Then for one value of x, we have two values of y.

This means that this is not a function.