Which set of ordered pairs is a function?

a. (1,2) (3,4) (5,6) (3,-4)
b. (8,4) (4,3) (2,2) (8,1)
c. (2,5) (3,10) (4,15) (5,20)
d. (2,4) (2,3) (2,1) (2,0)

OPTION C

Step-by-step explanation:

An element in the domain should be mapped to exactly one element on the co-domain. Also, every element in the domain should be mapped to an element in the co-domain.

These two conditions are satisfied to call a relation, a function.

Two different elements in the domain can be mapped to the same element in the co-domain. But the same element in the domain cannot be mapped to two different elements in the co-domain.

A) (1,2), (3,4), (5,6), (3,-4)

Here, the element '3' is mapped to 4 and -4. So, this is not a function.

B) (8,4), (4,3), (2,2), (8,1)

'8' is mapped to 4 and 1. So, it is not a function.

C) (2,5), (3,10), (4,15), (5,20)

All the elements in the domain are mapped to an element in the co-domain.  Also, every element in the domain has exactly one image in the co-domain. So, this relation is a function.

D) (2,4), (2,3), (2,1), (2,0)

The element '2' has more than one image. Clearly, it contradicts the definition of a function.

So, only OPTION C is the answer.

step-by-step explanation:

the ratio of red paint to blue paint is always 9/7. that means that, whatever x's value, (4x+12)/(4x-4) has that same ratio. so, set up an equation and cross-multiply to solve for x:

9/7 = (4x+12)/(4x-4)

9(4x-4) = 7(4x+12)

36x - 36 = 28x + 84

8x - 36 = 84

8x = 120

x = 15