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a) Ta có : 7/12 = 7*8/12*8 = 56/96
5/8 = 5*12/8*12 = 60/96
Vì 56 < 57 < 60 nên 56/96 < 57/96 < 60 / 96
Vậy phân số cần tìm là 57/96
b) Ta có : 7/12 = 7*8/12*8 = 56/96
5/8 = 5*12/8*12 = 60/96
Vì 56 < 57 ; 58 < 60 nên 56/96 < 57/96 ; 58/96 < 60/96
Vậy các phân số cần tìm là 57/96 và 58/96
c) Ta có : 7/12 = 7*24/12*24 = 168/288
5/8 = 5*36/8*36 = 180/288
Vì 168 < 169 ; 170 ; 171 ; 172 ; 173 ; 174 ; 175 ; 176 ; 177 < 180 nên 168/288 < 169/288 ; 170/288 ; 171/288 ; 172/288 ; 173/288 ; 174/288 ; 175/288 ; 176/288 ; 177/288 < 180/288
Vậy các phân số cần tìm là : 169/288 ; 169/288 ; 170/288 ; 171/288 ; 172/288 ; 173/288 ; 174/288 ; 175/288 ; 176/288 ; 177/288.
d) Gọi phân số cần tìm là y/15, ta có : 7/12 = 7*10/12*10 = 70/120
5/8 = 5*15/8*15 = 105/120
y/15 = y*8/15*8 = 8y/120
Vì 70 < 71 ; 72 ; 73 ; ..... ; 103 ; 104 < 105 nên 70/120 < 71/120 ; 72/120 ; 73/120 ; ..... ; 103/120 ; 104/120 < 105/120
=> y*8 thuộc {71 ; 72 ; 73 ; ..... ; 103 ; 104}
mà y*8 chia hết cho 8 nên y*8 thuộc {72 ; 80 ; 88 ; 96 ; 104}
y thuộc {9 ; 10 ; 11 ; 12 ; 13}
Vậy phân số cần tìm là : pick random 9 to 13/15
Ta có: \(A=\frac{1}{5}\left(\frac{5}{4.9}+\frac{5}{9.14}+......+\frac{5}{64.69}\right)\)
\(\Rightarrow A=\frac{1}{5}\left(\frac{1}{4}-\frac{1}{9}+\frac{1}{9}-\frac{1}{14}+......+\frac{1}{64}-\frac{1}{69}\right)\)
\(\Rightarrow A=\frac{1}{5}\left(\frac{1}{4}-\frac{1}{69}\right)=\frac{1}{5}\times\frac{65}{276}\)
\(\Rightarrow A=\frac{13}{276}\)
Vậy \(A=\frac{13}{276}\)
Ta có:-2/4=x/10=>4.x=-2.10=>4.x=-20=>x=-20:4=>x=-5
Thay x=-5 ta có:-5/10=-7/y=>10.(-7)=y.(-5)=>y.(-5)=-70=>y=-70:(-5)=>y=14
Thay y=14 ta có:-7/14=z/-24=>14.z=-24.(-7)=>14.z=168=>z=168:14=>z=12
Vậy x=-5;y=14;z=12
Đúng 100% luôn nha!
a)1.2.3.4...9-1.2.3.4...8-1.2.3.4...8.8
=1.2.3.4...8(9-1-8)
=1.2.3.4...8.0
=0
b)(3.4.216)2/11.123.411-169=(3.22.216)2/11.213.222-236=32.24.232/11.235-236=32.226/235.(11-2)
=32.236/235.9=32.236/235.32=2
c)70.(131313/565656+131313/727272+131313/909090
=70.(13/56+13/72+13/90)
=70.39/70=39
d)1/4.9+1/9.14+1/14.19+...+1/64.69
=4/4.9.4+4/9.4.14+4/14.19.4+...+4/64.69.4.
=1/4.(4/4.9+4/9.14+4/14.19+...+4/64.69)
=1/4.(1/4-1/9+1/9-1/14+1/14-1/19+...+1/64-1/69)
=1/4.(1/4-1/69)
=1/4.65/276=65/1104
~~~~~~~~Chúc bạn học giỏi nhé !~~~~~~~~
\(=\frac{3}{200}:\frac{3}{5}+\frac{3}{2}\left(\frac{4}{25}-\frac{2}{5}\right)-\frac{1}{25}.\left(\frac{7}{4}:\frac{7}{5}-\frac{5}{2}\right)\)
\(=\frac{3.5}{200.3}+\frac{3}{2}\left(\frac{4}{25}-\frac{2.5}{25}\right)-\frac{1}{25}\left(\frac{7.5}{4.7}-\frac{5}{2}\right)\)
\(=\frac{1}{40}+\frac{3}{2}\left(\frac{-6}{25}\right)-\frac{1}{25}\left(\frac{5}{4}-\frac{10}{4}\right)\)
\(=\frac{1}{40}-\frac{9}{25}+\frac{1}{20}\)
\(=\frac{1.5}{40.5}-\frac{9.8}{25.8}+\frac{1.10}{20.10}\)
\(=\frac{5-72+10}{200}=\frac{-57}{200}\)
\(\frac{8^2}{7.9}.\frac{9^2}{8.10}...\frac{14^2}{13.15}\)
\(\frac{8.8}{7.9}.\frac{9.9}{8.10}...\frac{14.14}{13.15}\)
\(\frac{8.9...14}{7.8...13}.\frac{8.9...14}{9.10...15}\)
\(\frac{14}{7}.\frac{8}{15}\)
\(2.\frac{8}{15}\)
\(\frac{16}{15}\)
(8.9.10.11.12.13.14)(8.9.10.11.12.13.14)/7.8.9.10.11.12.13).(9.10.11.12.13.14.15)
=14.8/7.15
=16/15
k cho mình nhá
\(A=\frac{5}{13}+\frac{-5}{7}+\frac{-20}{41}+\frac{8}{13}+\frac{-21}{41}\)
\(\Leftrightarrow A=\left(\frac{5}{13}+\frac{8}{13}\right)+\left(\frac{-20}{41}+\frac{-21}{41}\right)+\frac{-5}{7}\)
\(\Leftrightarrow A=1+\left(-1\right)+\frac{-5}{7}\)
\(\Leftrightarrow A=0+\frac{-5}{7}=\frac{-5}{7}\)
Vậy A = \(\frac{-5}{7}\)
B= \(\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{4}{-9}+\frac{7}{15}\)
\(\Leftrightarrow B=\frac{-5}{9}+\frac{8}{15}+\frac{-2}{11}+\frac{-4}{9}+\frac{7}{15}\)
\(\Leftrightarrow B=\left(\frac{-5}{9}+\frac{-4}{9}\right)+\left(\frac{8}{15}+\frac{7}{15}\right)+\frac{-2}{11}\)
\(\Leftrightarrow B=-1+1+\frac{-2}{11}\)
\(\Leftrightarrow B=0+\frac{-2}{11}\)
\(\Leftrightarrow\) \(B=\frac{-2}{11}\)
Vậy \(B=\frac{-2}{11}\)
@@ Học tốt
Chiyuki Fujito
K cần tk nhá
\(a)\) \(\frac{-11}{12}< \frac{x}{12}< \frac{-3}{4}\)
\(\Leftrightarrow\)\(\frac{-11}{12}< \frac{x}{12}< \frac{-9}{12}\)
\(\Leftrightarrow\)\(-11< x< -9\)
\(\Rightarrow\)\(x=-10\)
\(=\frac{108}{63}+\frac{105}{63}=\frac{108+105}{63}=\frac{213}{63}\)
\(\frac{12}{7}\)-\(\frac{-15}{9}\) = \(\frac{12}{7}\)+ \(\frac{15}{9}\) = \(\frac{108}{63}\)+ \(\frac{105}{63}\)= \(\frac{108+109}{63}\)= \(\frac{217}{63}\)= \(\frac{31}{9}\)
nguyễn thị thu huyền nhầm rồi 217/63 chứ