Given:
First term of an arithmetic sequence is 2.
Sum of first 15 terms = 292.5
To find:
The common difference.
Solution:
We have,
First term: 
Sum of first 15 terms: 
The formula of sum of first n terms of an AP is
![S_n=\dfrac{n}{2}[2a+(n-1)d]](https://tex.z-dn.net/?f=S_n%3D%5Cdfrac%7Bn%7D%7B2%7D%5B2a%2B%28n-1%29d%5D)
Where, a is first term and d is common difference.
Putting
, n=15 and a=2 in the above formula, we get
![292.5=\dfrac{15}{2}[2(2)+(15-1)d]](https://tex.z-dn.net/?f=292.5%3D%5Cdfrac%7B15%7D%7B2%7D%5B2%282%29%2B%2815-1%29d%5D)
![292.5=\dfrac{15}{2}[4+14d]](https://tex.z-dn.net/?f=292.5%3D%5Cdfrac%7B15%7D%7B2%7D%5B4%2B14d%5D)
![292.5=15[2+7d]](https://tex.z-dn.net/?f=292.5%3D15%5B2%2B7d%5D)
Divide both sides by 15.




Dividing both sides by 7, we get


Therefore, the common difference is 2.5.
Answer:
I think it's D
Step-by-step explanation:
Answer:
See below ~
Step-by-step explanation:
<u>Question 1</u>
⇒ -7x - (8x + 16) = -1
⇒ -7x - 8x - 16 = -1
⇒ -15x = 15
⇒ x = -1
⇒ y = 8(-1) + 16 = 8
⇒ Solution = <u>(-1, 8)</u>
<u></u>
<u>Question 2</u>
⇒ 3x + 4(-3x - 18) = 0
⇒ 3x - 12x - 72 = 0
⇒ -9x = 72
⇒ x = -8
⇒ y = -3(-8) - 18 = 6
⇒ Solution = <u>(-8, 6)</u>
<u>Question 3</u> (not clear)
<u>Question 4</u>
⇒ -8x - 7(6x) = 0
⇒ -8x - 42x = 0
⇒ -50x = 0
⇒ x = 0
⇒ y = 6(0) = 0
⇒ Solution = <u>(0, 0)</u>
<u>Question 8</u>
- 2x - 6y = -14
- y = -5x - 19
⇒ 2x - 6(-5x - 19) = -14
⇒ 2x + 30x + 114 = -14
⇒ 32x = -128
⇒ x = -4
⇒ y = -5(-4) - 19 = 1
⇒ Solution = <u>(-4, 1)</u>
which is similar to n:1 where 
<u>Step-by-step explanation:</u>
Here we have to Express in the form n:1 give n as a decimal 21:12 . Let's find out:
Given ratio as 21:12 . Let's convert it into n:1 , where n is decimal
⇒ 
⇒ 
⇒ 
⇒ 
⇒
{ dividing denominator & numerator by 4 }
⇒ 
⇒ 
⇒
which is similar to n:1 where 
True
Note that:

The graph of sine and cosine functions are very similar. They only have a shift in the x -axis.
That is, sin x = cos (90 - x)
Since there is a great similarity between the sine and cosine graphs, and the secant graph is an inverse of the cosine graph, the graph of sine can be used to construct the graph of the secant function
Mathematically:
since sec x = 1 / cos x
and, cos x = sin (90 - x)
therefore, sec x = 1 / sin (90 - x)
The graphs of the sine and secant functions are attached to this solution
Learn more here: brainly.com/question/9554579