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b) Quy luật: Số tiếp theo = Tổng 2 số liền trước
=> 1 + 4 + 5 + 9 + 14 + 23 + 37 + 60 + 97 = (1 + 4 + 5) + (23 + 23) + (97 + 97)
= 10 + 46 +194 = 250
\(5\frac{9}{10}:\frac{3}{2}-\left[2\frac{1}{3}\times4\frac{1}{2}-2\times2\frac{1}{3}\right]:\frac{7}{4}\)
\(=\frac{59}{10}:\frac{3}{2}-\left[\frac{7}{3}\times\frac{9}{2}-2\times\frac{7}{3}\right]:\frac{7}{4}\)
\(=\frac{59}{10}\times\frac{2}{3}-\left[\left(\frac{9}{2}-2\right)\times\frac{7}{3}\right]:\frac{7}{4}\)
\(=\frac{59}{10}\times\frac{2}{3}-\left[\frac{5}{2}\times\frac{7}{3}\right]:\frac{7}{4}\)
\(=\frac{59}{10}\times\frac{2}{3}-\frac{35}{6}:\frac{7}{4}\)
\(=\frac{59}{15}-\frac{35}{6}\times\frac{4}{7}\)
\(=\frac{59}{15}-\frac{221}{42}\)
\(=-\frac{93}{70}\)
Học tốt !
1. 41/7 - x = 25/9
=> x = 41/7 - 25/9
=> x = 194/63
2. 3x = 12,8
=> x = 12,8 : 3
=> x = 64/15
3. 41/2 x = 5
=> x = 5: 41/2
=> x = 10/41
4. 3/4 x = 1
=> x = 1: 3/4
=> x = 3/4
5. 4/5 : x = 3
=> x = 4/5 : 3
=> x = 4/15
6. 12/x = 4
=> x = 12/4
=> x = 3
7. 4/7 : x = 4/7
=> x = 4/7 : 4/7
=> x = 1
8. 2x - 3/4 = 7/8
=> 2x = 7/8 + 3/4
=> 2x = 13/8
=> x = 13/8 : 2
=> x =13/16
Ruby Chan :))
1, \(4\frac{1}{7}-x=2\frac{5}{9}\)
\(\frac{4\times7+1}{7}-x=\frac{2\times9+5}{9}\)
\(\frac{29}{7}-x=\frac{23}{9}\)
\(x=\frac{29}{7}-\frac{23}{9}\)
\(x=\frac{261}{63}-\frac{161}{63}\)
\(x=\frac{100}{63}\)
2, \(3\times x=12,18\)
\(x=12,18\div3\)
\(x=4,06\)
3, \(4\frac{1}{2}\times x=5\)
\(\frac{4\times2+1}{2}\times x=5\)
\(\frac{9}{2}\times x=5\)
\(x=5\div\frac{9}{2}\)
\(x=\frac{5\times2}{9}=\frac{10}{9}\)
4, \(\frac{3}{4}\times x=1\)
\(x=1\div\frac{3}{4}\)
\(x=\frac{1\times4}{3}=\frac{4}{3}\)
5, \(\frac{4}{5}\div x=3\)
\(x=\frac{4}{5}\div3\)
\(x=\frac{4}{5\times3}=\frac{4}{15}\)
6,\(\frac{12}{x}=4\)
\(x=12\div4\)
\(x=3\)
7, \(\frac{4}{7}\div x=\frac{4}{7}\)
\(x=\frac{4}{7}\div\frac{4}{7}\)
\(x=1\)
8, \(2x-\frac{3}{4}=\frac{7}{8}\)
\(2x=\frac{7}{8}+\frac{3}{4}\)
\(2x=\frac{7}{8}+\frac{6}{8}\)
\(2x=\frac{13}{8}\)
\(x=\frac{13}{8}\div2\)
\(x=\frac{13}{8\times2}=\frac{13}{16}\)
32,2857 và 12,8 và -498814315,3 và 0,1 và 11
tổng = - 498814259,1
`1/2x +( 2/4+3/6)= 4/5`
`=> 1/2x +( 12/24 + 12/24)=4/5`
`=> 1/2 x+ 24/24=4/5`
`=> 1/2 x+1=4/5`
`=>1/2x=4/5-1`
`=>1/2x= 4/5-5/5`
`=>1/2x= -1/5`
`=>x=-1/5 : 1/2`
`=>x=-1/5 xx 2`
`=>x=-2/5`
`--------`
`3/8 +x=2/5`
`=>x=2/5-3/8`
`=>x= 16/40 - 15/40`
`=>x=1/40`
`@ yl`
Đặt A = \(\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...+\frac{1}{1+2+3+...+10}\)
\(A=\frac{1}{\frac{2.3}{2}}+\frac{1}{\frac{3.4}{2}}+...+\frac{1}{\frac{10.11}{2}}\)
\(A=\frac{2}{2.3}+\frac{2}{3.4}+...+\frac{2}{10.11}\)
\(A=2.\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{10}-\frac{1}{11}\right)\)
\(A=2.\left(\frac{1}{2}-\frac{1}{11}\right)\)
\(A=2\cdot\frac{9}{22}=\frac{9}{11}\)
Vậy A = \(\frac{9}{11}\)
