Select the sets that are not functions.
a = {(1, 2), (2, 3), (3, 4), (4, 5)}
b = {(1, 2), (2, 1), (3, 0), (4, -1)}
c = [(-1, 3), (0, 3), (1, 3), (2, 3)}
d = {(1, 1), (1, 2), (1, 3), (1, 4);
e = {(6,2), (7,3), (6,-1), (5,4)}

D,E are not functions

Step-by-step explanation:

A function is a relation in which every  input has not more than one output.But the output of the inputs may be same.Here in D the input 1 has 4 different outputs as 1,2,3,4.So its not a function.Similarly in E 6 has 2 outputs as 2 and -1.For remaining sets the inputs has only one output.so they are functions.

answer: on graphs, the open and closed circles, or vertical asymptotes drawn as dashed lines us identify discontinuities.

as before, graphs and tables allow us to estimate at best.

when working with formulas, getting zero in the denominator indicates a point of discontinuity.

when working with piecewise-defined functions, check for discontinuities at the transition points where one piece ends and the next begins.

step-by-step explanation: