There is a rule:
One input(x-value) can only have one output(y-value) in order to be a function.
If one input has more than one output, it is not a function.
(This doesn't apply to outputs, one output can have more than one input and still be a function)
The 1st option is not a function because the inputs 9 and 10 have more than one output.
The 2nd option is not a function because the input 3 has more than one output.
The 3rd option is a function because each input only has one output.
The 4th option is not a function because the input 5 has more than one output.
ANSWER
• Circumference: 18.84 ft
,
• Area: 28.26 ft²
EXPLANATION
The circumference of a circle of radius r is,

In this case, the radius is r = 3 ft and we have to use 3.14 for π,

Hence, the circumference of this circle is 18.84 feet.
The area of a circle of radius r is,

In this case, r = 3 ft and π = 3.14,

Hence, the area of this circle is 28.26 square feet.
Sn = n(n+1) = 100(101) = 10100
Answer:
x=-2y-6
Step-by-step explanation:
Subtract 2y from both sides, and now you have x=-2y-6.