Can anyone help explain these questions? Will fan and medal (:

Describe how you can use the Vertical Line test to tell whether or not a given relation is a function.

Evaluate each function rule for x=-2.
a. f(x) = 4x

b. p(x) = ½x +2

c. g(x)=-2x-1

Question

Can anyone help explain these questions? Will fan and medal (: 

Describe how you can use the Vertical Line test to tell whether or not a given relation is a function.

Evaluate each function rule for x=-2.
a. f(x) = 4x 
 
b. p(x) = ½x +2 
 
c. g(x)=-2x-1

imstuck · Answer

If f(x) is a function, there is only one x value for every y.  A function fails the vertical line test if there are several y values for a single x value.  I'll attach an example in just a second.  As for the rest of the questions, f(-2) = 4x means you fill in -2 for every x.  So the first one is 4(-2) = -8.  The second one 1/2(-2) + 2 = 1.  The third one is -2(-2) -1 = 3.  |dw:1400821490362:dw|.  See?  The x value of 1 has lots of y values, and that just isn't legal in terms of functions!