First of all get a picture of what this looks like. Desmos is a pretty good graphing program, but anything that will do polar coordinates will work.
Here is the graph.
What you can see is that this graph is symmetrical around the x axis.
When you talk about symmetry, you can think of it as taking a mirror and putting it where you think there is symmetry. If you can't tell the difference between the image and the real thing, then you have symmetry.
In this case, the mirror will show symmetry along the x axis and no where else.
Answer:
1. 8/$12=21/$x then cross multiply.
2. 1/$1.5, we're looking for cost so $1 is more reasonable
3. $31.5
Step-by-step explanation:
12x 21/ 8 = 31.5
18 is the right answer. The two fractions must be porportional
First of all, we can observe that

So the expression becomes

This means that the expression is defined for every 
Now, since the denominator is always positive (when it exists), the fraction can only be positive if the denominator is also positive: we must ask

Since we can't accept 3 as an answer, the actual solution set is
![(-\infty,-2] \cup [2,3) \cup (3,\infty)](https://tex.z-dn.net/?f=%28-%5Cinfty%2C-2%5D%20%5Ccup%20%5B2%2C3%29%20%5Ccup%20%283%2C%5Cinfty%29)
B.) because according to the identity property of addition, any number added to zero will remain the same.