The square root of a circle would be your answer because 4.2-8
Answer:

f(x) = 4 when x is 8
Step-by-step explanation:
Domain is the set of x values that make the function defined. Allowed x values for the function (mapping).
The Range is the set of y values that make the function defined. Allowed y values for the function (mapping).
- Whenever we need to find f(a), suppose, then we look for "a" in the domain and see its corresponding value mapping in the range.
- Whenever we will be given a value for f(x) = a, suppose, and we have to find "x", we look at the value a in the range and find corresponding x value in the domain.
Firstly, we need f(4), so we look for "4" in domain and see which number it corresponds to in range.
That is 
Thus,

Next,
We want "x" value that gives us a "y" value of 4. We look for "4" in the range and see which value it corresponds to. That is "8". So,
f(8) = 4
We can identify that the missing reason in the proof is: Definition of Congruent angles.
<h3>How to give proof of a congruent triangle?</h3>
We know that an angle measure of 90° of ∠ABC in the triangle means that it is a right angle triangle.
We also see that ∠ADB is also a right angle and is equal to 90°.
Now, since they have exactly the same measure, these angles are congruent. Then we can say that the angles are congruent and as such:
∠ABC ≅ ∠ABD
Thus, we can identify that the missing reason is: Definition of Congruent angles.
Read more about Triangle proof at; brainly.com/question/1248322
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1) 18
2) 4
3) 27
4) 9
5) x=8
6) x=6