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\(P=\frac{1}{5x8}+\frac{1}{8x11}+.....+\frac{1}{602x605}\)
\(\Rightarrow3P=\frac{3}{5x8}+\frac{3}{8x11}+......+\frac{3}{602x605}\)
\(\Rightarrow3P=\frac{1}{5}-\frac{1}{8}+\frac{1}{8}-.....+\frac{1}{602}-\frac{1}{605}\)
\(\Rightarrow3P=\frac{1}{5}-\frac{1}{605}\)
\(\Rightarrow3P=\frac{24}{121}\)
\(\Rightarrow P=\frac{24}{121}:3\)
\(\Rightarrow P=\frac{8}{121}\)
\(\frac{16x17-5}{16x16+11}=\frac{16x16+16-5}{16x16+11}=1\)
\(\frac{4}{3x7}+\frac{5}{7x12}+\frac{1}{12x13}+....+\frac{3}{20x23}\)
=\(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{12}+\frac{1}{12}-\frac{1}{13}+...+\frac{1}{20}-\frac{1}{23}\)
=\(\frac{1}{3}-\frac{1}{23}=\frac{20}{69}\)
a) \(\frac{16\cdot17-5}{16\cdot16+11}\)
= \(\frac{16\cdot16+16-5}{16\cdot16+11}\)
= \(\frac{16\cdot16+11}{16\cdot16+11}=1\)
\(\left(\frac{3}{10}+\frac{1}{5}+\frac{2}{15}\right):3\)
\(=\left(\frac{9}{30}+\frac{6}{30}+\frac{4}{30}\right):3\)
\(=\frac{19}{30}:3\)
\(=\frac{19}{30}.\frac{1}{3}\)
\(=\frac{19}{90}\)
\(\left(\frac{3}{10}+\frac{1}{5}+\frac{2}{15}\right):3\)
\(=\frac{19}{30}:3\)
\(=\frac{19}{30}.\frac{1}{3}\)
\(=\frac{19}{90}\)
a) \(\frac{7}{9}\)< 1 còn \(\frac{9}{7}\)> 1
Vậy \(\frac{7}{9}< \frac{9}{7}\)
b) Ta rút gọn phân số \(\frac{3535}{4848}\)= \(\frac{35}{48}\)
\(\frac{35}{48}\)và \(\frac{5}{8}\)MSC: 48
Ta có:
Giữ nguyên phân số \(\frac{35}{48}\) \(\frac{5}{8}=\frac{5x6}{8x6}=\frac{30}{48}\)
Vì \(\frac{35}{48}>\frac{30}{48}\)nên \(\frac{3535}{4848}>\frac{5}{8}\)
a) ta có : 7/9 <1 và 9/7 > 1 => 7/9 < 9/7
b) 3535/4848 = 35/48
ta có 5/ 8 = 30/48
=> 3535/4848> 5/8
\(\frac{1}{3x7}+\frac{1}{7x11}+.....+\frac{1}{Xx\left(Xx4\right)}=\frac{5}{63}\)
Ai nhanh mk tik nha!
Ta có:
\(\frac{1}{3.7}+\frac{1}{7.11}+\frac{1}{11.15}+...+\frac{1}{x.\left(x+4\right)}=\frac{5}{63}\)
\(=\frac{1}{4}.\left(\frac{4}{3.7}+\frac{4}{7.11}+\frac{4}{11.15}+...+\frac{4}{x.\left(x+4\right)}\right)=\frac{5}{63}\)
\(\Rightarrow\left(\frac{1}{3}-\frac{1}{7}+\frac{1}{7}-\frac{1}{11}+\frac{1}{11}-\frac{1}{15}+....+\frac{1}{x}-\frac{1}{x+4}\right)=\frac{5}{63}:\frac{1}{4}\)
\(\Rightarrow\frac{1}{3}-\frac{1}{x+4}=\frac{20}{63}\Leftrightarrow\frac{1}{x+4}=\frac{1}{63}\Leftrightarrow x=63-4=59\)
\(\frac{2}{3}+\frac{5}{8}+\frac{9}{3}:\frac{4}{7}.\left(\frac{2}{6}+\frac{1}{1}\right)\)
\(=\frac{2}{3}+\frac{5}{8}+3:\frac{4}{7}.\left(\frac{1}{3}+1\right)\)
\(=\frac{2}{3}+\frac{5}{8}+\frac{21}{4}.\frac{4}{3}\)
\(=\frac{2}{3}+\frac{5}{8}+7\)
\(=\frac{16}{24}+\frac{15}{24}+7\)
\(=\frac{31}{24}+7\)
\(=\frac{19}{12}\)
Mình không biết đúng hay sai, nhưng mà kết bạn nha!
1. \(\frac{3}{1.4}+\frac{3}{4.7}+\frac{3}{7.10}+...+\frac{3}{40.43}\)
\(=1-\frac{1}{4}+\frac{1}{4}-\frac{1}{7}+\frac{1}{7}-\frac{1}{10}+...+\frac{1}{40}-\frac{1}{43}\)
\(=1-\frac{1}{43}\)
\(=\frac{42}{43}\)
2. Đặt \(A=\frac{2}{2}+\frac{2}{6}+\frac{2}{12}+...+\frac{2}{90}\)
\(=2.\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{9.10}\right)\)
\(=2.\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{9}-\frac{1}{10}\right)\)
\(=2.\left(1-\frac{1}{10}\right)\)
\(=2.\frac{9}{10}\)
\(=\frac{9}{5}\)
Ủng hộ mk nha !!! ^_^
1) 3/1×4 + 3/4×7 + 3/7×10 + ... + 3/40×43
= 1 - 1/4 + 1/4 - 1/7 + 1/7 - 1/10 + ... + 1/40 - 1/43
= 1 - 1/43
= 42/43
2) 2/2 + 2/6 + 2/12 + ... + 2/90
= 2 × (1/2 + 1/6 + 1/12 + ... + 1/90)
= 2 × (1/1×2 + 1/2×3 + 1/3×4 + ... + 1/9×10)
= 2 × (1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + ... + 1/9 - 1/10)
= 2 × (1 - 1/10)
= 2 × 9/10
= 9/5
Ai tk mình đi mình bị âm rồi!
Ai tk mình mình tk lại!
nhanh giúp mình đi các bạn,nếu giúp mình mà đúng thì mình tk cho