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\(1\dfrac{4}{5}+2\dfrac{5}{7}+3\dfrac{4}{5}+4\dfrac{5}{7}\)
\(\text{=}\left(1\dfrac{4}{5}+3\dfrac{4}{5}\right)+\left(2\dfrac{5}{7}+4\dfrac{5}{7}\right)\)
\(\text{=}1+3+\left(\dfrac{4}{5}+\dfrac{4}{5}\right)+2+4+\left(\dfrac{5}{7}+\dfrac{5}{7}\right)\)
\(\text{=}10+\dfrac{8}{5}+\dfrac{10}{7}\text{=}131\dfrac{1}{35}\)
\(1\dfrac{1}{2}x1\dfrac{1}{3}x1\dfrac{1}{4}x1\dfrac{1}{5}x1\dfrac{1}{6}x1\dfrac{1}{7}x1\dfrac{1}{8}x1\dfrac{1}{9}\)
\(=\dfrac{3}{2}x\dfrac{4}{3}x\dfrac{5}{4}x\dfrac{6}{5}x\dfrac{7}{6}x\dfrac{8}{7}x\dfrac{9}{8}x\dfrac{10}{9}\)
\(=x^7.\dfrac{3.4.5.6.7.8.9.10}{2.3.4.5.6.7.8.9}\)
\(=x^7.\dfrac{10}{2}\)
\(=5x^7\)
\(=\dfrac{3}{2}\times\dfrac{4}{3}\times\dfrac{5}{4}\times...\times\dfrac{9}{8}\times\dfrac{10}{9}=\dfrac{10}{2}=5\)
1.
a) 8,4
b) 0,0245
2.
\(\dfrac{3}{5}+\dfrac{1}{2}+\dfrac{3}{10}\)\(=\dfrac{6}{10}+\dfrac{5}{10}+\dfrac{3}{10}\)
\(=\dfrac{6+5+3}{10}\)
\(=\dfrac{14}{10}=...\)
\(\frac{38}{11}+\frac{4}{17}-\frac{5}{11}-\frac{3}{17}\)
\(=\frac{38}{11}-\frac{5}{11}+\frac{4}{17}-\frac{3}{17}\)
\(=\frac{33}{11}+\frac{1}{17}\)
\(=3+\frac{1}{17}\)
\(=\frac{52}{17}\)
38/11+4/17-5/11-3/17
=(38/11-5/11)+(4/17-3/17)
=3+1/17
=51/17+1/17=52/17
`a, 2/3 +3/4 = (8+9)/12=17/12.`
`1 1/3+4/5 = 4/3 + 4/5 = (20+12)/15=32/15`.
`=> x=2.`
`b, 5/6-1/4=(20-6)/24=7/12`.
`2 1/3-2/5= 7/3-2/5 = (35-6)/15=29/15`.
`=> x=1`.
Số số hạng của dãy là : \(\left(45-1\right)\div4+1=12\)( số )
Ta có :
\(\left(x+1\right)+\left(x+5\right)+\left(x+9\right)+....+\left(x+45\right)=331,2\)
\(\Leftrightarrow12\times x+\frac{\left(45+1\right)\times12}{2}=331,2\)
\(\Leftrightarrow12\times x+276=331,2\)
\(\Leftrightarrow12\times z=55,2\)
\(\Leftrightarrow x=4,6\)
Vậy \(x=4,6\)
\(x-15\%x=170\)
\(x-\frac{15}{100}x=170\)
\(x\left(1-\frac{15}{100}\right)=170\)
\(x.\frac{85}{100}=170\)
\(x=170:\frac{85}{100}\)
\(x=200\)
\(x-15\%x=170\)
\(\Rightarrow x-\frac{15}{100}x=170\)
\(\Rightarrow x\left(1-\frac{15}{100}\right)=170\)
\(\Rightarrow x\times\frac{85}{100}=170\)
\(\Rightarrow170:\frac{85}{100}\)
\(\Rightarrow x=200\)
a/\(x-\dfrac{5}{7}-\dfrac{13}{14}=1\)
\(x=1+\dfrac{5}{7}+\dfrac{13}{14}\)
\(x=\dfrac{14}{14}+\dfrac{10}{14}+\dfrac{13}{14}\)
\(x=\dfrac{37}{14}\)
Vậy \(x=\dfrac{37}{14}\)
b/\(\dfrac{3}{5}+x+1\dfrac{1}{5}=\dfrac{11}{3}\)
\(x+\dfrac{3}{5}+\dfrac{6}{5}=\dfrac{11}{3}\)
\(x+\dfrac{9}{5}=\dfrac{11}{3}\)
\(x=\dfrac{11}{3}-\dfrac{9}{5}\)
\(x=\dfrac{55}{15}-\dfrac{27}{15}\)
\(x=\dfrac{28}{15}\)
Vậy \(x=\dfrac{28}{15}\)
#kễnh
a) \(x-\dfrac{5}{7}-\dfrac{13}{14}=1\)
\(x-\dfrac{23}{14}=1\)
\(x=1+\dfrac{23}{14}\)
\(x=\dfrac{37}{14}\)
b) \(\dfrac{3}{5}+x+1\dfrac{1}{5}=\dfrac{11}{3}\)
\(x+1+\dfrac{3}{5}+\dfrac{1}{5}=\dfrac{11}{3}\)
\(x+\dfrac{9}{5}=\dfrac{11}{3}\)
\(x=\dfrac{11}{3}-\dfrac{9}{5}\)
\(x=\dfrac{28}{15}\)
1.7 km2 2 ha =7,02 km2
2.4/5ha = 8000 m2
7,02 km2 câu 2 8000 m2