a-68=(3 và 10/11-4):(2121/2222-1):(33333/343434-1)
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a ) \(x+7\frac{4}{5}=9\frac{7}{15}\)
\(x+\frac{39}{5}=\frac{142}{15}\)
\(x=\frac{142}{15}-\frac{39}{5}\)
\(x=\frac{5}{3}\)
b ) \(x-4\frac{9}{11}=\frac{2121}{2222}\)
\(x-\frac{53}{11}=\frac{21}{22}\)
\(x=\frac{21}{22}+\frac{53}{11}\)
\(x=\frac{127}{22}\)
x - 4\(\dfrac{9}{11}\) = \(\dfrac{2121}{2222}\)
\(x+7\dfrac{4}{5}=9\dfrac{7}{15}\)
\(=>x+\dfrac{39}{5}=\dfrac{142}{15}\)
\(=>x=\dfrac{142}{15}-\dfrac{39}{5}=\dfrac{142}{15}-\dfrac{117}{15}\)
\(=>x=\dfrac{25}{15}=\dfrac{5}{3}\)
___________
\(x-4\dfrac{9}{11}=\dfrac{2121}{2222}\)
\(=>x-\dfrac{53}{11}=\dfrac{21}{22}\)
\(=>x=\dfrac{21}{22}+\dfrac{53}{11}=\dfrac{21}{22}+\dfrac{106}{22}\)
\(=>x=\dfrac{127}{22}\)
\(x+7\dfrac{4}{5}=9\dfrac{7}{15}\)
\(x=9\dfrac{7}{15}-7\dfrac{4}{5}\)
\(x=\left(9-7\right)+\left(\dfrac{7}{15}-\dfrac{4}{5}\right)\)
\(x=2\dfrac{-1}{3}=\dfrac{5}{3}\)
\(x=\dfrac{2121:101}{2222:101}+4\dfrac{9}{11}\)
\(x=\dfrac{21}{22}+4\dfrac{18}{22}\)
\(x=\dfrac{21+4\cdot22+18}{22}=\dfrac{127}{22}\)
a, 2
22
+ 222
2222
22222
2 x 5 + 2x 4 x 10 + 2 x 3 x 100 + 2 x 2 x 1000 + 2 x 1 x 10000
2 x (5+4x10+3x100+2x1000+1x10000)
2x [5x100 + (5-1)x101 + (5-2) x102 + (5-3) x103 + (5-4) x104]
Ta có công thức: Nếu số hạng là các chữ số n và có m số hạng:
n x (mx100 + (m-1)x101 + (m-2) x102 +……….+2 x 10m-2 + 1x10m-1
Tính tổng trên:
2 x (10x1 + 9x10 + 8x100 + 7x1000 + 6x10000 + 5x100000 + …+ 1x10000000000) =
2 x (10+90+800+7000+60000+500000+4000000+30000000+200000000+1000000000) =
2 x 1234567900 = 2 469 135 800
b, tương tự câu a,
\(a-68=\left(3\frac{10}{11}-4\right):\left(\frac{2121}{2222}-1\right):\left(\frac{33333}{343434}-1\right)\)
\(a-68=\left(\frac{43}{11}-4\right):\left(\frac{-1}{22}\right):\left(\frac{-310101}{343434}\right)\)
\(a-68=\frac{-1}{11}.\frac{-22}{1}.\frac{-343434}{310101}\)
\(a-68=\frac{1}{11}.\frac{22}{1}.\frac{343434}{310101}.\left(-1\right)\)
\(a-68=\frac{-686868}{310101}\)
\(a=\frac{-686868}{310101}+68\)
\(a=\frac{-20400000}{310101}\)
Vậy \(a=\frac{-20400000}{310101}\)
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