a.
In order to find the common ratio, we just need to divide a term by the term that comes before it.
So using the terms 20 and -5, we have:

b.
The recursive rule can be found with the formula:

Where an is the nth term and q is the ratio. So we have:

c.
The explicit rule can be written as:

Where an is the nth term, a1 is the first term and q is the ratio. So:

Substitute the values of x, y and z to the expression:

Answer:
undefined. No one knows the answer. ¯\_(ツ)_/¯¯
The answer is
X^2+y^2+Dx+Ey+F=0
Answer:
x = 2√3
Step-by-step explanation:
The sides of a 30-60-90 triangle are always in the ratio 1:√3:2.
The length of the side opposite the 90° angle is 4, so the length of the side opposite the 30° angle is 2 and the length of the side opposite the 60° angle is 2√3.
x = 2√3