Số số hạng của tổng B:
      (6,95 - 5,15) : 0,2 + 1 = 10 (số hạng)

B = (6,95 + 5,15) x 10 : 2 = 60,5

`@` `\text {Ans}`

`\downarrow`

`a)`

`13/50 + 9% + 41/100 + 0,24`

`= 0,26 + 0,09 + 0,41 + 0,24`

`= (0,26 + 0,24) + (0,09 + 0,41)`

`= 0,5 + 0,5`

`= 1`

`b)`

`2018 \times 2020 - 1/2017 + 2018 \times 2019`

`= 2018 \times (2020 + 2019) - 1/2017`

`= 2018 \times 4039 - 1/2017`

`= 8150702`

`c)`

`1/2 + 1/6 + 1/12 + 1/20 +1/30 +1/42`

`=`\(\dfrac{1}{1\times2}+\dfrac{1}{2\times3}+\dfrac{1}{3\times4}+\dfrac{1}{4\times5}+\dfrac{1}{5\times6}+\dfrac{1}{6\times7}\)

`=`\(1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{6}-\dfrac{1}{7}\)

`=`\(1-\dfrac{1}{7}\)

`= 6/7`

\(a,\dfrac{13}{50}+9\%+\dfrac{41}{100}+0,24\\ 0,26+0,09+0,41+0,24\\ =\left(0,26+0,24\right)+\left(0,09+0,41\right)\\ =0,5+0,5\\ =1\\ b,2018\times2020-\dfrac{1}{2017}+2018\times2019\\ =2018\times\left(2020+2019\right)-\dfrac{1}{2017}\\ =2018\times4039-\dfrac{1}{2017}\\ =3150702-\dfrac{1}{2017}\\ c,\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}\\ =1-\dfrac{1}{2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\\ =1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}.........+\dfrac{1}{6}-\dfrac{1}{7}\\ =1-\dfrac{1}{7}\\ =\dfrac{6}{7}\)

16,5

Thank bạn :))))))

a: Sửa đề:\(4,89\cdot4,5+4,89\cdot4,5+4,89\)

\(=4,89\cdot\left(4,5+4,5+1\right)\)

\(=4,89\cdot10=48,9\)

b: \(0,123\cdot7800+1,23\cdot220\)

\(=1,23\cdot780+1,23\cdot220\)

\(=1,23\left(780+220\right)\)

\(=1,23\cdot1000=1230\)

c: \(0,4\cdot0,45\cdot2,5\)

\(=0,4\cdot2,5\cdot0,45\)

\(=1\cdot0,45=0,45\)

d: \(0,2\cdot5,55\cdot50\)

\(=0,2\cdot50\cdot5,55\)

\(=5,55\cdot10=55,5\)

   77 x 5,55 + 60,12 x 7,45 + 16,88 x 7,45
= 77 x 5,55 + 7,45 x ( 60,12 + 16,88 )
= 77 x 5,55 + 7,45 x 77
= 77 x ( 5,55 + 7,45 )
= 77  x  13
=  1001

77 NHÉ KO PHẢI 75 MÌNH GHI NHẦM

\(\frac{159,8}{2,35}=\frac{15980}{235}=68\) 

Chia hết luôn bạn nk 

Vì đề con viết thiếu nên cô đã sửa nhé.

Ta có \(S=1-2+2^2-2^3+...-2^{2017}\)

\(\Rightarrow4S=2^2.S=2^2\left(1-2+2^2-2^3+...-2^{2017}\right)\)

\(\Rightarrow4S=2^2-2^3+2^4-2^5+...-2^{2017}+2^{2018}-2^{2019}\)

\(\Rightarrow4S=S+1+2^{2018}-2^{2019}\)

\(\Rightarrow3S=1+2^{2018}-2^{2019}\)

\(\Rightarrow M=3S-2^{2018}=1-2^{2019}\)

làm gif có a/b mà tính

a/A=|x-2017|+|x-2018|

     =|x-2017|+|2018-x|

=>Alớn hơn hoặc bằng |x-2017+2018-x|=1

Dấu = xảy ra khi:(x-2017+2018-x) lớn hơn hoặc bằng 0

Vậy GTNN của A=1khi 2017 nhỏ hơn hoặc bằng x nhỏ hơn hoặc bằng 2018