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Bài làm
\(A=\left[\left(\frac{2}{193}-\frac{3}{386}\right).\frac{193}{17}+\frac{33}{34}\right]:\left[\left(\frac{7}{2001}+\frac{11}{4002}\right).\frac{2001}{25}+\frac{9}{2}\right]\)
\(=\left[\frac{1}{386}.\frac{193}{17}+\frac{33}{34}\right]:\left[\frac{25}{4002}.\frac{2001}{25}+\frac{9}{2}\right]\)
\(=\left[\frac{1}{34}+\frac{33}{34}\right]:\left[\frac{1}{2}+\frac{9}{2}\right]\)
\(=\frac{1}{5}\)
a)Ta có:
\(A=\left(\frac{1}{2^2}-1\right)\left(\frac{1}{3^2}-1\right)\left(\frac{1}{4^2}-1\right)....\left(\frac{1}{98^2}-1\right)\left(\frac{1}{99^2}-1\right)\)
\(=\left(\frac{1}{2.2}-1\right)\left(\frac{1}{3.3}-1\right)\left(\frac{1}{4.4}-1\right)....\left(\frac{1}{98.98}-1\right)\left(\frac{1}{99.99}-1\right)\)
\(=\left(-\frac{3}{2.2}\right).\left(-\frac{8}{3.3}\right).\left(-\frac{15}{4.4}\right)...\left(-\frac{9603}{98.98}\right).\left(-\frac{9800}{99.99}\right)\)
\(=\left[\left(-1\right).\left(-1\right).\left(-1\right)...\left(-1\right)\right].\frac{3}{2.2}.\frac{8}{3.3}.\frac{15}{4.4}...\frac{9603}{98.98}.\frac{9800}{99.99}\)
|------------------------98 số -1--------------------|
\(=\left(-1\right)^{98}.\frac{1.3}{2.3}.\frac{2.4}{3.3}.\frac{3.5}{4.4}...\frac{95.97}{98.98}.\frac{98.100}{99.99}\)
\(=\frac{1.3}{2.3}.\frac{2.4}{3.3}.\frac{3.5}{4.4}...\frac{95.97}{98.98}.\frac{98.100}{99.99}\)
\(=\frac{1.3.2.4.3.5...95.97.98.100}{2.2.3.3.4.4...98.98.99.99}\)
Ta sẽ rút gọn các thừa số chung ở tử và mẫu
\(=\frac{1.100}{2.99.99}\)
\(=\frac{50}{9801}\)
Vậy \(A=\frac{50}{9801}\)
cho mik hỏi bước 3 chỗ \(\frac{3}{2.2}\)sai o duoi lai la\(\frac{3}{2.3}\)vay
B= (2/3-1/4+5/11):(5/12+1-7/11)
B=(8/12-3/12+5/11):(5/12+1-7/11)
B=(5/12+5/11):(5/12+1-7/11)
B=115/132:(17/12-7/11)
B=115/132:103/132
B=115/103
Mik làm mẫu cho 1 con nè. các câu sau cxn tương tự từ trái wa phải.Nều bạn tính toán kém thì cứ làm như câu mẫu trên. Mik mà làm bài này thì mik làm theo cách nhanh hơn cơ. Chúc bạn học tốt và có 1 ngày tốt lành nghen. Có j cần giúp đỡ thì cứ bảo mik
a: \(=\dfrac{17}{7}+\dfrac{2}{9}-\dfrac{10}{7}-\dfrac{5}{3}\cdot9=1+\dfrac{2}{9}-15=-14+\dfrac{2}{9}=-\dfrac{126}{9}+\dfrac{2}{9}=-\dfrac{124}{9}\)
b: \(=\dfrac{-11}{23}\left(\dfrac{6}{7}+\dfrac{8}{7}\right)-\dfrac{1}{23}=\dfrac{-22}{23}-\dfrac{1}{23}=-1\)
c: \(=\left(\dfrac{377}{-231}-\dfrac{123}{89}+\dfrac{34}{791}\right)\cdot\dfrac{4-3-1}{24}=0\)
d: \(=\dfrac{12}{7}\left(19+\dfrac{5}{8}-15-\dfrac{1}{4}\right)=\dfrac{12}{7}\cdot\dfrac{35}{8}=\dfrac{15}{2}\)
2: \(=\dfrac{0.8}{\dfrac{16}{25}-\dfrac{1}{25}}+\dfrac{\dfrac{71}{75}\cdot\dfrac{7}{4}}{\dfrac{119}{36}\cdot\dfrac{36}{17}}\)
\(=\dfrac{4}{5}\cdot\dfrac{5}{3}+\dfrac{71}{300}=\dfrac{471}{300}=\dfrac{157}{100}\)
3: \(=\dfrac{\dfrac{2}{5}-\dfrac{2}{9}+\dfrac{2}{11}}{\dfrac{7}{5}-\dfrac{7}{9}+\dfrac{7}{11}}-\dfrac{\dfrac{2}{6}-\dfrac{2}{8}+\dfrac{2}{10}}{\dfrac{7}{6}-\dfrac{7}{8}+\dfrac{7}{10}}\)
=2/7-2/7=0
Ta có : [ ( 2/193 - 3/386 ) * 193/17 + 32/34 ] : [ ( 7/2001 + 11/4002 ) * 2001/25 + 9/2 ] .
=> [ 2/193 * 193/17 - 3/386 * 193/17 + 32/34 ] : [ 7/2001 * 2001/25 + 11/4002 * 2001/25 + 9/2 ] .
=> [ 2/17 - 3/34 + 32/34 ] : [ 7/25 + 11/50 + 9/2 ] .
=> [ 4/34 - 3/34 + 32/34 ] : [ 14/50 + 11/50 + 225/50 ] .
=> 33/34 : 5 .
=> 33/34 * 1/5 .
=> 33/170 .
Tính bằng cách thuận tiện nhất:
\(=\left[\left(\frac{2}{193}\cdot\frac{193}{17}\right)-\left(\frac{3}{386}\cdot\frac{193}{17}\right)+\frac{32}{34}\right]:\left[\left(\frac{7}{2001}\cdot\frac{2001}{25}\right)+\left(\frac{11}{4002}\cdot\frac{2001}{25}\right)+\frac{9}{2}\right]\)
\(=\left[\left(\frac{2}{17}-\frac{3}{17}\right)+\frac{32}{34}\right]:\left[\left(\frac{7}{25}+\frac{11}{50}\right)+\frac{9}{2}\right]\)
\(=\left(-\frac{1}{17}+\frac{32}{34}\right):\left(\frac{1}{2}+\frac{9}{2}\right)\)
\(=\frac{15}{17}+5\)
\(=\frac{100}{17}\)
~ học tốt ~