[2/11.13+2/13.15+2/15.17+2/17.19+2/19.20].462-x=19
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ND
1
27 tháng 2 2016
=(1/11-1/13)+(1/13-1/15)+(1/15-1/17)+(1/17-1/19)+(1/19-1/21)*462-X=19
=(1/11-1/21)*462-X=19
=10/231*462-X=19
=20-X=19
=X=20-19
=X=1
lop nam cung lam duoc
20 tháng 6 2018
\(\left(\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+\frac{2}{17.19}+\frac{2}{19.21}\right)\) ) . 462 - x = 19
\(\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+\frac{1}{19}-\frac{1}{21}\right)\) . 462 - x = 19
\(\left(\frac{1}{11}-\frac{1}{21}\right)\) . 462 - x = 19
... Chúc bạn học tốt !
20 tháng 6 2018
\(\left(\frac{2}{11\cdot13}+\frac{2}{13\cdot15}+\frac{2}{15\cdot17}+\frac{2}{17\cdot19}+\frac{2}{19\cdot21}\right)\)\(\cdot462-x=19\)
\(\left(\frac{1}{11\cdot13}+\frac{1}{13\cdot15}+\frac{1}{15\cdot17}+\frac{1}{17\cdot19}+\frac{1}{19\cdot21}\right)\)\(\cdot462-x=19\)
\(\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+\frac{1}{19}-\frac{1}{21}\right)\)\(\cdot462-x=19\)
\(\left(\frac{1}{11}-\frac{1}{21}\right)\cdot462-x=19\)
\(\frac{10}{231}\cdot462-x=19\)
\(20-x=19\)
\(x=20-19\)
\(x=1\)
ND
0
NN
0
NM
1
2 tháng 3 2019
\(\left(\frac{2}{11.13}+\frac{2}{13.15}+...+\frac{2}{19.21}\right).462-\left[2,04:\left(x+1,05\right):0,12\right]=19\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+...+\frac{1}{19}-\frac{1}{21}\right).462-\left[2,04:\left(x+1,05\right):0,12\right]=19\)
\(\Leftrightarrow\left(\frac{1}{11}-\frac{1}{21}\right).462-\left[2,04:\left(x+1,05\right):0,12\right]=19\)
\(\Leftrightarrow\frac{10}{231}.462-\left[2,04:\left(x+1,05\right):0,12\right]=19\)
\(\Leftrightarrow20-\left[2,04:\left(x+1,05\right):0,12\right]=19\)
\(\Leftrightarrow2,04:\left(x+1,05\right):0,12=1\)
\(\Leftrightarrow2,05:\left(x+1,05\right)=0,12\)
\(\Leftrightarrow x+1,05=\frac{205}{12}\)
\(\Leftrightarrow x=\frac{205}{12}-1,05\)
\(\Leftrightarrow x=\frac{481}{30}\)
Đặt \(A=\frac{2}{11.13}+\frac{2}{13.15}+\frac{2}{15.17}+\frac{2}{17.19}+\frac{2}{19.21}^{ }\)
\(A=\frac{1}{11}-\frac{1}{13}+\frac{1}{13}-\frac{1}{15}+\frac{1}{15}-\frac{1}{17}+\frac{1}{17}-\frac{1}{19}+\frac{1}{19}-\frac{1}{21}\)
\(A=\frac{1}{11}-\frac{1}{21}\)
\(A=\frac{10}{231}\)
Thay \(A=\frac{10}{231}\) vào ta có
\(\frac{10}{231}.462-x=19\)
\(20-x=19\)
\(x=20-19\)
\(x=1\)
boi vi\(\frac{10}{231}.462=20\) cho mik dung nha