# Math

posted by on .

Select the relation that is a function.
a.
{(21, 11), (21, 10), (21, 9), (21, 8)}
c.
{(-6, -5), (3, 2), (10, 8), (3, 3)}
b.
{(-2, -1),(5, -1), (16, 3), (-3, -9)}
d.
{(5, 10), (-3, 10), (-3, -10), (4, 7)}

• Math - ,

hint: each element must have a single image.

• Math - ,

• Math - ,

cause i don't understand what you saying

• Math - ,

Note that in (a) (21,11) and (21,10) indicate that f(21) = 11 and f(21) = 10.
That can't be so, for a function.

In (c), we have f(3) = 2 and f(3) = 3

In (b) there is only one mapping for each element.

In (d) we have f(-3)=10 and f(-3)=-10.

each element can have only one image under the mapping. That is, the relation maps the first value to the second value in each pair.

A value can only be mapped to a single image. Better study the chapter on relations, mapping, images, etc. and what makes a function more restrictive than just a general relation.

• Math - ,

so b?

• Math - ,

That'd be my guess, unless you have b and c switched. They are listed out of order.