Which of the following expressions represents a function? (5 points)

x = 1
{(3, 2), (3, −2), (4, 5), (4, −5)}
y = 4x − 1
4x2 + y2 = 16

Question

Which of the following expressions represents a function? (5 points)

 	
	x = 1
	{(3, 2), (3, −2), (4, 5), (4, −5)}
	y = 4x − 1
	4x2 + y2 = 16

iwillrektyou · Answer

A function must start with either f(x), or y.

anonymous · Answer

So itd either be a or c?

iwillrektyou · Answer

It would be c. The reason is:
x = 1, is just a point.
{(3,2),(3, -2), (4, 5), (4, -5)} is a series of points.
y = 4x - 1 starts with y, and has a slope and y-intercept.
4x^2 + y^2 = 16 is just an equation.

anonymous · Answer

OMG thank you so much.

iwillrektyou · Answer

No problem!

danjs · Answer

x = 1 is a line
a series of points can also be a function, but that one has more than one y value for a given x value so it is not. 
The third is a line and is a function.
the fourth is an Ellipse, and is nto a function for the same reasons, more than one y value for a given x

anonymous · Answer

Thanks!

danjs · Answer

If the graph of any of them ever cross a vertical line more than once, Not a function.. quick visual test...