Answer:
225
Step-by-step explanation:
The sum of this series is given by the formula:
![S_n=\frac{n}{2}[2a+(n-1)d]](https://tex.z-dn.net/?f=S_n%3D%5Cfrac%7Bn%7D%7B2%7D%5B2a%2B%28n-1%29d%5D)
Where
S_n is the sum
a is the first term (we get this by plugging in n = 1 into "2n-1", we have 2(1) - 1 = 1)
n is the number of terms (the sum is defined for n = 1 to n = 15, so 15 terms)
d is the common different (the difference is successive terms. Here, 2nd term would be 2(2) - 1 = 3, and first term was 1, so d = 3 -1 = 2)
<em>plugging in the info, we will get the sum:</em>
<em>![S_n=\frac{n}{2}[2a+(n-1)d]\\S_{15}=\frac{15}{2}[2(1)+(15-1)(2)]\\=225](https://tex.z-dn.net/?f=S_n%3D%5Cfrac%7Bn%7D%7B2%7D%5B2a%2B%28n-1%29d%5D%5C%5CS_%7B15%7D%3D%5Cfrac%7B15%7D%7B2%7D%5B2%281%29%2B%2815-1%29%282%29%5D%5C%5C%3D225)
</em>
<em>The sum is 225</em>
Answer: 25x^2 - 1^2
Explanation:
(5x+1) (5x-1)
(5x)^2 - 1^2
25x^2 - 1^2
7 + 3.(2 - 3x) = 67
3 brackets are distributed
7+6-9x = 67
13-9x = 67
-9x = 67
x = 67/-9
Answer:
7.9
4.2
9.3
17.8
Step-by-step explanation:
8. √63
the square of 8 is 64 √63 is close to 64 so we can say it's 7.9 approximately
9. √18
the square of 4 is 16, √18 is greater than 16 so we can say it's 4.2 approximately
10. √87
the square of 9 is 81, √87 is greater than 81 so we can say the value of it is approximately 9.3
11. √319
the square of 18 is 324, √319 is smaller than 324 so we can say it's 17.8
1/9 = 2/18 = 3/27 = 4/36 = 5/45 = ... = n/(9n) for any n
