1/2+3/4+5/6+7/8+9/10+…… +199/200=

1/2+3/4+5/6+7/8+9/10+…… +199/200=

The original formula = (1-1 / 2) + (1-1 / 4) + +（1-1/200）
=100-(1/2+1/4+1/6+.1/200)=100-1/2*(1+1/2+1/3+.+1/100)
Then = Sn in brackets
Sn＝1＋（1－1／2）＋（1－2／3）＋（1－3／4）＋…… ＋（1－ 99／100）
The sum of all 1 is 100, and the general term formula of the remaining sequence is an = n / (n + 1), then the splitting term can be eliminated

Finding matrix multiplication formula
Please write the formula of multiplication of two matrices in detail. Thank you
For example:
1 2 1 2 3 4
A = 2 5 3 B = 1 5 2
1 3 4 3 6 7
A * B = ?
Please write the calculation process in detail, I will add points. Thank you!

.1*2+2*1+1*3..1*3+2*5+1*6..1*4+2*2+1*7..7.19.15
A*B=2*2+5*1+3*3..2*3+5*5+3*6..2*4+5*2+3*7=18.49.39
.1*2+3*1+4*3..1*3+3*5+4*6..1*4+3*2+4*7..17.42.38
... denotes a space
The rule is to multiply the i-th row of the preceding matrix and the j-th column of the following matrix and add them to the (I, J) position of the resulting matrix
See?

40% of a number is 18 times more than 1.2 times of 30

40%x-30X1.2=18
40%x-36=18
40%x=54
x=135

It is known that 224-1 can be divided by two integers between 60 and 70, then the two integers are______ And______ ．

224-1, = (212) 2-1, = (212 + 1) (212-1), = (212 + 1) [(26) 2-1], = (212 + 1) (26 + 1) (26-1), where (26 + 1) (26-1) is 65 and 63, so the two integers are 65 and 63

1277 the middle plus sign equals 24

﹙7×7－1﹚÷2=24

Is there a rational number whose absolute value is negative

No
The absolute value is either positive or zero
There are no negative numbers

A story book has 56 pages. Xiaomin read 2 / 7 of all the stories on the first day and 4 / 7 of all the stories on the second day. How many pages did she read on the first day and her brother read on the second day?

Hanying warm for you
first day:
56 × 2 / 7 = 16 pages
the second day:
56 × 4 / 7 = 32 pages
(or click "satisfied" in the upper right corner of the client)
It's my motivation to move forward! Your adoption will also bring you wealth value
If you don't understand,
Until the completion of understand this problem!

The perimeter of an isosceles triangle is 26cm, and the perimeter of an isosceles triangle with its waist as its side is 30cm?

26-30÷3x2
=26-20
=6
The bottom is 6cm

It takes 10 hours for the bus to complete the whole journey, and 15 hours for the truck to complete the whole journey. After the two cars meet on the way, the bus runs another 96 kilometers. At this time, the bus runs 20% of the whole journey. How many kilometers is the distance between the two places?

The distance between a and B is x km, and the meeting time is t hours
VX = x / 10
V = x / 15
(x/10+x/15)t=x
So t = 6 hours
x/10*t+96=(1-20%)x
solve equations:
X = 120 km
Brother problem, should be when the bus line, the whole 20%

2014 power of (negative 5 / 13) * (negative 2 / 3 right 5 / 5)

(negative five out of thirteen) to the power of 2014 * (negative two and three out of five) to the power of 2015
=-(5 / 13) to the power of 2014 * (13 / 5) to the power of 2015
=-(5 / 13) to the power of 2014 * (13 / 5) to the power of 2014 * (13 / 5)
=-(5 / 13 * 13 / 5) to the power of 2011 * (13 / 5)
=-1*(13/5)
=-13/5
This is my conclusion after meditation,
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