Câu 1:

57x26+57x43+57x31

= 57x(26+43+31)

= 57x100

=5700

Câu 2:

177x 56- 56x56+ 121x44

= (177-56)x 56+ 121x44

= 122x56 + 121x44

= 121x(56+44)

=121x100

=12100

\(57.26+57.43+57.31\)

\(=57.\left(26+43+31\right)\)

\(=57.100\)

\(=5700\)

\(177.56-56.56+121.44\)

\(=56.\left(177-56\right)+121.44\)

\(=56.121+121.44\)

\(=121.\left(56+44\right)\)

\(=121.100\)

\(=12100\)

\(68.42+34.16\)

\(=34.2.42+34.16\)

\(=34.84+34.16\)

\(=34\left(84+16\right)\)

\(=34.100\)

\(=3400\)

Rut gon :

2x -6/8-6/56-6/140-6/260=43/52 

                         2x-12/13 =43/52             

                                  2x   =43/52+12/13

                                    x    = 7/4 : 2

                                    x     = 7/8

a) 

\(=\frac{7\cdot7\cdot8\cdot8\cdot9\cdot9\cdot10\cdot10\cdot11\cdot11}{6\cdot8\cdot7\cdot9\cdot8\cdot10\cdot9\cdot11\cdot10\cdot12}\)    

\(=\frac{7\cdot11}{6\cdot12}\)     

\(=\frac{77}{72}\)

b) 

\(=1+\frac{1}{6}+1+\frac{1}{12}+1+\frac{1}{20}+1+\frac{1}{30}+1+\frac{1}{42}+1+\frac{1}{56}\)  

\(=6+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}\)  

\(=6+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{8}\)  

\(=6+\frac{1}{2}-\frac{1}{8}\)  

\(=6+\frac{3}{8}\)

\(=\frac{51}{8}\)

Chia thành...a và b nhé.

Bg

a)Ta có: \(\frac{49}{48}.\frac{64}{63}.\frac{81}{80}.\frac{100}{99}.\frac{121}{120}\)

= \(\frac{49.64.81.100.121}{48.63.80.99.120}\)

= \(\frac{7.7.8.8.9.9.10.10.11.11}{6.8.7.9.8.10.9.11.10.12}\)

= \(\frac{7.11}{6.12}\)    (chịt tiêu trên dưới)

= \(\frac{77}{72}\)

b) Ta có: \(\frac{7}{6}+\frac{13}{12}+\frac{21}{20}+\frac{31}{30}+\frac{43}{42}+\frac{57}{56}\)

Có 6 số hạng  (đếm)

= \(1+\frac{1}{6}+1+\frac{1}{12}+1+\frac{1}{20}+1+\frac{1}{30}+1+\frac{1}{42}+1+\frac{1}{56}\)

= \(1+1+...+1+\frac{1}{6}+\frac{1}{12}+\frac{1}{20}+\frac{1}{30}+\frac{1}{42}+\frac{1}{56}\)

= \(1.6+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)

= \(6+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}+\frac{1}{6}-\frac{1}{7}+\frac{1}{7}-\frac{1}{8}\)

= \(6+\frac{1}{2}-\frac{1}{8}\)

= \(\frac{13}{2}-\frac{1}{8}\)

= \(\frac{51}{8}\)

Hơi dài....

THANK YOU

\(318-5\left(x-64\right)=103\)

\(\Rightarrow5\left(x-64\right)=318-103\)

\(\Rightarrow5\left(x-64\right)=215\)

\(\Rightarrow x-64=43\)

\(\Rightarrow x=43+64\)

\(\Rightarrow x=107\)

_____________

\(4^x\cdot5+216=296\)

\(\Rightarrow4^x\cdot5=296-216\)

\(\Rightarrow4^x\cdot5-80\)

\(\Rightarrow4^x=16\)

\(\Rightarrow4^x=4^2\)

\(\Rightarrow x=2\)

___________

\(376-6^x:3=364\)

\(\Rightarrow6^x:3=376-364\)

\(\Rightarrow6^x:3=12\)

\(\Rightarrow6^x=36\)

\(\Rightarrow6^x=6^2\)

\(\Rightarrow x=2\)

___________

\(\left(4x-1\right)^2=121\)

\(\Rightarrow\left(4x-1\right)^2=11^2\)

\(\Rightarrow\left[{}\begin{matrix}4x-1=11\\4x-1=-11\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}4x=12\\4x=-10\end{matrix}\right.\)

\(\Rightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{5}{2}\end{matrix}\right.\)

107

2

2

TH1: 3; TH2: -5/2

318 x 72 + 159 x 2 x 28

= 318 x 72 + 318 x 28

= 318 x (72 + 28) = 318 x 100 = 31800

159 x 2 x 72 + 159 x 56 

= 159 x ( 144 + 56 ) 

= 159 x 200 

= 31800

  318 x 72 + 159 x 2 x 28  = 318 x 72 + 318 x 28  = 318 x (72 + 28) = 318 x 100 = 31800

a) (x – 45).27 = 0 ó x – 45 = 0 ó x = 45

b) 41.(2x – 8).13 = 0 ó 2x – 8 = 0 ó x = 4

c) (x – 36):18 = 12 ó x – 36 = 12.18 ó x = 216 + 36 ó x = 252

d) 43.(x – 18) = 86 ó x – 18 = 86:43 ó x = 2+18 ó x = 20

e) 96 : (121 – x) = 4 ó 121 – x = 96 : 4 ó 121 – x = 24 ó x =      121 – 24 ó x = 97

f) 340 : (15x+5) = 17 ó 15x + 15 = 340 :17 ó 15x + 5 = 20 ó 15x = 20 – 5 ó 15x = 15 ó x = 1

\(2x+1+\frac{1}{6}+1+\frac{1}{12}+..+1+\frac{1}{90}=10\)

=> 2x + 8 + \(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}=10\)

=> 2x + \(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}=10-8\)

\(2x+1-\frac{1}{10}=2\)

=> 2x + \(\frac{9}{10}=2\)

=> 2x          = 2 - 9/10

=>2x           = 11/10 

=> x              = 11/10 : 2

x                  =  11/20 

thang Tran ơi,2x+1-1/10 ở đâu vậy

Phải là 2x+1/2-1/10 chứ

mk giải cho nè nhớ tích nha

2x+7/6+13/12+21/20+31/30+43/42+57/56+73/72+91/90=10

2x+(1/6+1)+(1/12+1)+(1/20+1)+(1/30+1)+(1/42+1)+(1/56+1)+(1/72+1)+(1/90+1)=10

2x+(1+1+1+1+1+1+1+1)+(1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90)=10

2x+8+(1/2+3+1/3+4+1/4+5+1/5+6+1/6+7+1/7+8+1/8+9+1/9+10)=10

2x+8+(1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10)=10

2x+8+(1/2-1/10)=10

2x+8+2/5=10

2x=10-8-2/5

2x=1,6

x=1,6:2

x=0,8

Mk thấy đề bài hơi dư nên x mk tìm ra là số thập phân còn đổi lại ra phân số là 4/5

\(\frac{-21}{5}\)

x= -127/30 .

gợi ý các bạn chọn ( k) đúng cho mình 

2x+7/6+13/12+21/20+31/30+43/42+57/56+73/72+91/90=10

2x+1+1/6+1+1/12+1+1/20+1+1/30+1+1/42+1+1/56+1+1/72+1+1/90=10

2x+(1+1+1+1+1+1+1+1)+(1/2.3+1/3.4+1/4.5+1/5.6+1/6.7+1/7.8+1/8.9+1/9.10)=10

2x+8+(1-1/2+1/2-1/3+...+1/9-1/10)=10

2x+1-1/10=10-8

2x+9/10=2

2x=2-9/10

2x=11/10

x=11/10/2

x=11/20

đáp án là 4/5