Answer:
Explained below.
Step-by-step explanation:
Consider the series is a set of first 6 natural numbers.
Sum of first <em>n</em> terms is:



Consider the series is an arithmetic sequence.
Sum of first <em>n</em> terms is:
![S_{n}=\frac{n}{2} [2a+(n-1)d]](https://tex.z-dn.net/?f=S_%7Bn%7D%3D%5Cfrac%7Bn%7D%7B2%7D%20%5B2a%2B%28n-1%29d%5D)
Here<em>,</em>
<em>a</em> = first term
<em>d</em> = common difference
Consider the series is an geometric sequence.
Sum of first <em>n</em> terms is:

Here<em>,</em>
<em>a₁</em> = first term
<em>r</em> = common ratio
Answer:
By virtue of the Pythagorean Theorem, in a right triangle the sum of the squares of the smaller two sides equals the square of the largest side. Only 9, 12, and 15 fit this rule.
A triangle's angles will always equal up to 180. Since you already have to of the angles, you will add them up together. 30+20=50. Then, you take 180 and subtract it by the sum of the two previous angles. 180-50=130. Now you know the last angle is 130. You also know that the missing angle is also 130. The reason for that is because the two angles are the exact same if you look at it.
3(-2) -(1) -3(-2)
= -6 -1 +6 = -1