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TA CÓ ;
\(A=\frac{3}{4}.\frac{8}{9}...\frac{2499}{2500}\)
\(A=\frac{1.3}{2.2}.\frac{2.4}{3.3}...\frac{49.51}{50.50}\)
\(A=\frac{1.3.2.4...49.51}{2.2.3.3...50.50}\)
\(A=\frac{\left(1.2...49\right).\left(3.4...51\right)}{\left(2.3...50\right).\left(2.3...50\right)}\)
\(A=\frac{1.51}{50.2}=\frac{51}{100}\)
VẬY \(A=\frac{51}{100}\)
= 3/4 x 8/9 x 15/16 x ... x 9999/10000
= 3 x 8 x 15 x ... x 9999/ 4 x 9 x 16 x ... x 10000
= (1 x 3) x (2 x 4) x (3 x 5) x ... x (99 x 101)/ (2 x 2) x (3 x 3) x (4 x 4) x ... x (100 x 100)
= (1 x 2 x 3 x ... x 99) x (3 x 4 x 5 x ... x 101)/ (2 x 3 x 4 x ... x 100) x (2 x 3 x 4 x ... x 100)
= (1 x 2 x 3 x ... x 99) x (3 x 4 x 5 x ... x 101)/ (2 x 3 x 4 x ... x 100) x (2 x 3 x 4 x ... x 100)
= 1x 101/ 100 x 2
= 101/200
CHÚC BN HOK TỐT ^^
\(B=\frac{3}{4}\cdot\frac{8}{9}\cdot\frac{15}{16}\cdot\cdot\cdot\cdot\frac{2499}{2500}=\frac{1.3}{2.2}\cdot\frac{2.4}{3.3}\cdot\frac{3.5}{4.4}\cdot\frac{49.51}{50.50}\)
\(=\frac{1.2.3....49}{2.3.4...50}\cdot\frac{3.4.5...51}{2.3.4...50}=\frac{1}{50}\cdot\frac{51}{2}=\frac{51}{100}\)
\(\frac{1\cdot3}{2\cdot2}\cdot\frac{2\cdot4}{3\cdot3}\cdot\frac{3\cdot5}{4\cdot4}\cdot...\cdot\frac{99\cdot101}{100\cdot100}\)
\(\frac{1\cdot101}{2\cdot100}\)
\(\frac{101}{200}\)
\(x^3=16x\)
\(\Leftrightarrow x^3-16x=0\)
\(\Leftrightarrow x\left(x^2-16\right)=0\)
\(\Leftrightarrow\orbr{\begin{cases}x=0\\x^2-16=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=0\\x=\pm4\end{cases}}\)
\(=\frac{2.4}{3^2}.\frac{3.5}{4^2}....\frac{49.51}{50^2}\)
\(=\frac{2.3....49}{3.4....50}.\frac{4.5....51}{3.4....50}\)
\(=\frac{2}{50}.\frac{17}{1}\)
\(=\frac{17}{25}\)
Ta có : \(A=\frac{8}{9}.\frac{15}{16}.....\frac{2499}{2500}\)
\(A=\frac{8.15.....2499}{9.16.....2500}\)
\(A=\frac{\left(2.4\right).\left(3.5\right).....\left(49.51\right)}{\left(3.3\right).\left(4.4\right).....\left(50.50\right)}\)
\(A=\frac{\left(2.3....49\right).\left(4.5....51\right)}{\left(3.4....50\right).\left(3.4.....50\right)}\)
\(A=\frac{2\left(3.4.....49\right).\left(4.5.....50\right).51}{\left(3.4.....49\right).50.3.\left(4.5.....50\right)}\)
\(A=\frac{2.51}{3.50}\)
\(A=\frac{2.17.3}{3.25.2}\)
\(A=\frac{17}{25}\)
A= 3/4x8/9x15/16x.......x 2499/2500
A=\(\frac{3}{4}x\frac{2.4}{3.3}x\frac{3.5}{4.4}x...x\frac{49.51}{50.50}\)
A=\(\frac{3x2x4x3x5x...x49x51}{4x3x3x4x4x...x50x50}\)
A=\(\frac{2x51}{4x50}\)
A=\(\frac{51}{100}\)
A= \(=\frac{3\times1}{2\times2}\times\frac{4\times2}{3\times3}\times\frac{3\times5}{4\times4}\times....\times\frac{49\times51}{50\times50}\)
\(=\frac{3\times1\times4\times2\times3\times5\times....\times49\times51}{2\times2\times3\times3\times4\times4\times....\times50\times50}\)
xong loai di nhung so o dang trc va nhan vs 51/50 va ra kq
xin loi vik ko lam het vik qua ban mong chon mik