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:
Let us consider the expression:
(1)
Now, the quotient of power rules says that the numbers that have same base can be find by subtracting if powers are with same sign
And adding if powers are with opposite sign.
We will solve equation (1) by this quotient of power rule.
So, it can be rewritten as:

.
Answer:
1. x=y−2
2. -1/2y + 4
Step-by-step explanation:
The answer is B 803.8cm^2