Find the first n terms and Sn of sequence {n + 1 / 3 ^ n + 1}

Find the first n terms and Sn of sequence {n + 1 / 3 ^ n + 1}

Sn=a1+a2+~+an=1+1/3^1+1+2+1/3^2+1+~+n+1/3^n+1=n(1+n)/2+[1/3×(1-1/3^n)]/(1-1/3)+n
=(n^2-1/3^n+3n+1)/2

[(a + b) × 2] square - [(a-b) × 2] square

[ ( a + b ) / 2 ]" - [ ( a - b ) / 2 ]"
= [ ( a + b )" / 4 ] - [ ( a - b )" / 4 ]
= ( 1/4 )[ ( a + b )" - ( a - b )" ]
= ( 1/4 )( a + b + a - b )( a + b - a + b )
= ( 1/4 )( 2a )( 2b )
= ab

The travel problem of a mathematical problem in grade one of junior high school
It is known that a circular track is 400 meters long. A runs 240 meters per minute and B 250 meters per minute
(1) Party A and Party B run in opposite directions at the same time. How long did they first meet?
(2) A and B run in the same direction at the same time. How long did they first meet?
(3) After that, B starts to run. How long can b catch up with a?
(4) B runs for one minute first, then a starts to run. How long can a catch up with B?
Use the equation of first degree with one variable!
Do not tell me that there is no solution if there is a positive solution

1) Let X minutes meet 240x + 250x = 400
2) Let X minutes meet 250x-240x = 400
3) Let X minutes catch up with 240 times (1.5 + x) = 250x
4) Let X minutes catch up with 250 (x + 1) - 400 = 240x

The famous Fibonacci sequence is as follows: 1, 1, 2, 3, 5, 8, 13, 21... What is the remainder of the 2008 number / 3?

Divide each by three
The remainder are: 1, 1, 2, 0, 2, 2, 1, 0, 1, 1, 2, 0, 2, 2, 1, 0
It can be found that the remainder is in the cycle of [1,1,2,0,2,2,1,0], 8 in a cycle
2008÷8=251
In other words, the 2008 remainder is the last number of the 251st cycle
This number is zero

Given that a plus B minus 6B plus 9 equals 0, find the value of B to the power of A

A (3a-4) of unit1
IV. complete the dialogue with each word empty
Sally:Joe ,where__ 16_ you five years ago?
Joe:Er ,in Xi'an.
Sally:What__ 17__ you be in ten years?
Joe:I 'll be a doctor.
Sally:Where__ 18___ you want to work?
Joe:I 'm not sure.Maybe in Dalian or Qingdao.How about you,Sally?
Sally:I want to be a flight attendant and then I _ 19___ __ 20___ able to travel around the world.
Joe:How wonderful!
16:_____ 17:_____ 18:______ 19.______ 20._______ Fill in the blanks with the proper form of the given words
1.Today he ___ (be) a middle school student.Three years ago he___
2.There___ (not be)a football match next week.
3.There will be more tall___ (build)in the cities.
4.Jane is a good student.She always___ (get)toschool early.
5.They are going to____ (travel)to Hangzhou next week.

were
will
do
am
be
is
was
won't be
buildings
gets
travel
It should be almost there

There are 76 red, white and blue glass balls of the same size, which are always arranged in the order of 2 red balls, 3 blue balls and 4 white balls?
I will take your advice

2+3+4=9
76 △ 9 = 8 and 4
So:
Number of blue balls = 8 × 3 + (4-2) = 26

How many grams of water is 1 ml water, 1 l

1 g, 1000 g

The average score of Xiaohong's Chinese, math and English is 94. She got 90 in Chinese. How many in math and English? What's the average score of math English?

94 × 3-90, = 282-90, = 192 (points); a: 192 for math and English. 192 △ 2 = 96 (points); a: the average score for math and English is 96

Students from the chemistry interest group of a university found that there is a layer of scale on the bottom of a long-term hot water kettle, and the main components of the scale are calcium carbonate and magnesium hydroxide. In order to determine the content of calcium carbonate in the scale, they added 10% hydrochloric acid to 12.5g scale to produce CO2 gas, as shown in the figure below
(1) It can be seen from the figure that the maximum amount of carbon dioxide generated by the reaction of 12.5g scale and hydrochloric acid is g
(2) What is the mass fraction of calcium carbonate in scale?
(3) It is assumed that the scale does not contain any impurities except calcium carbonate and magnesium hydroxide. To dissolve 12.5 g of scale, at least 10% hydrochloric acid is needed (the final result remains one decimal place)
Let the mass of calcium carbonate in 12.5g scale be X
The CaCO3 + 2HCl = CaCl2 + H2O + CO2 = CaCl2 + H2O + CO2, caccacl2 + H2O + CO2 = CaCl2 + H2O + CO2 = CaCl2 + H2O + CO2 8226; ;; 8226; ; ; 8226; 8226; ; ; \; \; \\; \\; \\\8226; \\\\\\\\\\\\\\\\\\\\\1point
100 44
x 3.3g
As a result of 100 × 3.3g (3 × 3.3g) of 3.3g, it was 7.5G (3 × 3.3g) and the results were as follows: 7.5G ; ; \; \\\\\\\\\8226; \\\\\;;;; \\\\\\\\\\\\\\\\\\\\\\\\\\point for the score of ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; ﹣ 8226; 1 point
7.5 g
The mass fraction of calcium carbonate in the scale is: -- × 100% = 60% & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; & ﹥ 8226; 1 point
12.5 g
(3) The results of 117.7 g were shown in this paper, and the results were as follows: 8226;; 8226;;; 8226;;; 8226;;;;; 8226;; 8226;; \\\\\\\\\;;; \;; \\\8226;;;;; \\\\\\\\\\\\\\\\\\\\\\\\\; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; & # 8226; 1 point

The molecular weight of calcium chloride is 111 instead of 44. You should write it at CO2. Third, ask CaCO3 + 2HCl = = CaCl2 + H2O + CO2 ↑ 100 737.5 y to get y = 6.293 g Mg (OH) 2 + 2HCl = MgCl2 + 2h2o58 735 Z to get z = 5.475 and 12.5 g salt of scale reaction