Sequence sum 2 / 3! + 3 / 4! + 4 / 5! +... + 99 / 100!

Sequence sum 2 / 3! + 3 / 4! + 4 / 5! +... + 99 / 100!

n/(n+1)!=[(n+1)-1]/(n+1)!
=1/n!-1/(n+1)!.
I don't understand

Linear algebra cuts a line from matrix A to get matrix B, and finds the relationship between the rank of a and B

Rank(B)=Rank(A)
If a is an invertible square matrix, one must be subtracted if one row is crossed out,
Rank(B)=Rank(A)-1
If the line of a is linearly related to the previous lines (which means that the line can be expressed linearly by the previous lines), then its rank is not changed
Such as a=
[
1 2 3
4 5 6
5 7 9
]
B=[
1 2 3
4 5 6
]
It's of equal rank

How many boats did the school rent for the students to row in the spring outing? If each boat takes 3 people, there will be one more boat. If each boat takes 5 people, there will be 19 people vacant. How many people are there?

3(x-1)=5x-19
3x-3=5x-19
2x=16
x=8
Eight ships, 21 people

lim（ x→0）sin2x / tan3x

Using the equivalent infinitesimal, when x → 0, sin2x → 2x, tan3x → 3x, the result is 2 / 3

Given that f (x) is an odd function with the domain R, and f (1) = 0, if x > 0, 2f (x) + XF '(x) > 0, then the solution set of inequality f (x) > 0 is
The known result is (- 1,0) U (1, + ∞),

Let g (x) = x ^ 2F (x) g '(x) = 2xf (x) + x ^ 2F' (x) ∵ when x > 0, 2f (x) + XF '(x) > 0 ∵ when x > 0, G' (x) > 0; when x > 1, f (x) > 0; when 1 > x > 0, f (x) > 0; when f (x) x > - 1, f (x) > 0

English translation
I'm in a hurry

What's this in English?

How many square meters is 10 mu of land equal to

10 mu = 666.6667 square meters

Solve the equation x / 1 * 2 + X / 2 * 3 + +x/99*100=99.

x/1*2+x/2*3+… +x/99*100=99
x(1/1*2+1/2*3+...+1/99*100)=99
x(1-1/2+1/2-1/3+...+1/99-1/100)=99
x(1-1/100)=99
x(99/100)=99
x=99*(100/99)
x=100

Seek English words and meanings of brands
Shufujia, inkle, naas, radar, giante, Youngor, Nike, Lenovo, lux, piaoluo, tide. Quick answer

Safeguard
incalcu
Cnnice
radar
Giant
Youngor
Nike
Lenovo
Lux
Rejoice
Tide

Let the sum of the first n terms of the arithmetic sequence an be Sn, and A4 + A8 > 0
Feeling 3 is right, 2 must be wrong, how to judge the other two

The arithmetic sequence {an}, the sum of the first n terms is Sn, and A4 + A8 = 2A6 > 0
∴ S11=11*(a1+a11)/2=11a6>0,S6-S5=a6＞0
Other conditions are insufficient to judge