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\(\Leftrightarrow2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+...+\frac{1}{x\left(x+1\right)}\right)=\frac{2008}{2010}\)
\(\Leftrightarrow2\left(\frac{3-2}{2.3}+\frac{4-3}{3.4}+\frac{5-4}{4.5}+...+\frac{\left(x+1\right)-x}{x\left(x+1\right)}\right)=\frac{2008}{2010}\)
\(\Leftrightarrow2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{x}-\frac{1}{x+1}\right)=\frac{2008}{2010}\)
\(\Leftrightarrow\frac{1}{2}-\frac{1}{x+1}=\frac{1004}{2010}\)
\(\Leftrightarrow\frac{1}{x+1}=\frac{1}{2010}\)
\(\Leftrightarrow x+1=2010\)
\(\Leftrightarrow x=2009\)
Tìm \(x\) câu a:
\(\frac13.x\) + \(\frac25.\left(x+1\right)\) = 0
\(\frac{5}{15}x\) + \(\frac{6}{15}x\) + \(\frac25\) = 0
\(\frac{11}{15}x\) = - \(\frac25\)
\(x=-\frac25:\frac{11}{15}\)
\(x\) = - \(\frac25\times\frac{15}{11}\)
\(x\) = - \(\frac{6}{11}\)
Vậy \(x=-\frac{6}{11}\)
Tìm \(x\) câu b:
\(x\) x 25% = 0,5
\(x\times0,25\) = 0,5
\(x=0,5:0,25\)
\(x=2\)
Vậy \(x=2\)
Câu 1a:
1/3x + 2/5(x + 1) = 0
1/3x + 2/5x + 2/5 = 0
1/3x + 2/5x = - 2/5
x(1/3 + 2/5) = -2/5
x.(5/15 + 6/15) = -2/5
x.11/15 = - 2/5
x = - 2/5 : 11/15
x = - 6/11
Vậy x = -6/11
Câu b:
x . 25%. x = 0,5
x.x = 0,5 : 25%
x^2 = 2
x = - \(\sqrt2\); x = \(\sqrt2\)
Vậy x ∈ {- \(\sqrt2\); \(\sqrt2\) )
Câu 1a:
1/3x + 2/5(x + 1) = 0
1/3x + 2/5x + 2/5 = 0
1/3x + 2/5x = - 2/5
x(1/3 + 2/5) = -2/5
x.(5/15 + 6/15) = -2/5
x.11/15 = - 2/5
x = - 2/5 : 11/15
x = - 6/11
Vậy x = -6/11
Câu b:
x . 25%. x = 0,5
x.x = 0,5 : 25%
x^2 = 2
x = - \(\sqrt2\); x = \(\sqrt2\)
Vậy x ∈ {- \(\sqrt2\); \(\sqrt2\) )
1/4+2/5+6/8+2/15+6/7
=(1/4+6/8)+(2/5+2/15)+6/7
=(2/8+6/8)+(6/15+2/15)+6/7
=1+8/15+6/7
=1+56/105+90/105
=1+146/105
=1+105/105+41/105
=1+1+41/105
=2+41/105
=2 và 41/105
2 và 41/105 là hỗn số nha
1/4+2/5+6/8+2/15+6/7
Ta có:
1/4=1-3/4
6/8=3/4
2/15=2/3*5=1/3-1/5
==> 1-3/4+2/5+3/4+1/3-1/5+6/7
=1+1/3+1/5+6/7
=(105+35+21+90)/105
=251/105.
\(0,5.1\frac{1}{3}.75\%:\frac{2}{5}+\frac{3}{5}\)
\(=\frac{1}{2}.\frac{4}{3}.\frac{3}{4}:\frac{2}{5}+\frac{3}{5}\)
\(=\frac{1}{2}.\frac{4}{3}.\frac{3}{4}.\frac{5}{2}+\frac{3}{5}\)
\(=\frac{5}{4}+\frac{3}{5}\)
\(=\frac{37}{20}\)
\(0,5.1\frac{1}{3}.75\%:\frac{2}{5}+\frac{3}{5}\)
\(=\frac{1}{2}.\frac{4}{3}.\frac{3}{4}:\frac{2}{5}+\frac{3}{5}\)
\(=\frac{1}{2}.\frac{4}{3}.\frac{3}{4}.\frac{5}{2}+\frac{3}{5}\)
\(=\frac{1.4.3.5}{2.3.4.2}+\frac{3}{5}\)
\(=\frac{5}{4}+\frac{3}{5}\)
\(=\frac{37}{20}\)
~Học tốt~
Ta có: 75%.x + \(\frac{1}{5}\).x = \(\frac{1}{6}\)
\(\frac{3}{4}\cdot x+\frac{1}{5}\cdot x=\frac{1}{6}\)
\(x\left(\frac{3}{4}+\frac{1}{5}\right)=\frac{1}{6}\)
\(\frac{19}{20}x=\frac{1}{6}\)
\(x=\frac{1}{6}:\frac{19}{20}=\frac{10}{57}\)
tích nha
75%.x+1/5.x=1/6 3/4.x+1/5.x=1/6 x.(3/4+1/5)=1/6 : x.19/20=1/6 suy ra x=1/6:19/20=1/6.20/19=10/57
\(75\%.x+\frac{1}{5}x=\frac{1}{6}\)
\(\Rightarrow\frac{3}{4}x+\frac{1}{5}x=\frac{1}{6}\)
\(\Rightarrow\left(\frac{3}{4}+\frac{1}{5}\right)x=\frac{1}{6}\)
\(\Rightarrow\left(\frac{15}{20}+\frac{4}{20}\right)x=\frac{1}{6}\)
\(\Rightarrow\frac{19}{20}x=\frac{1}{6}\)
\(\Rightarrow x=\frac{1}{6}:\frac{19}{20}\)
\(\Rightarrow x=\frac{1}{6}.\frac{20}{19}=\frac{10}{57}\)
\(\frac{3}{4}\).x + \(\frac{1}{5}\).x = \(\frac{1}{6}\)
(\(\frac{3}{4}\)+ \(\frac{1}{5}\)) . x = \(\frac{1}{6}\)
\(\frac{19}{20}\).x = \(\frac{1}{6}\)
x = \(\frac{1}{6}\): \(\frac{19}{20}\)
x = \(\frac{10}{57}\)
\(75\%\times x+\frac{1}{5}\times x=\frac{1}{6}\)
\(\Rightarrow\frac{3}{4}\times x+\frac{1}{5}\times x=\frac{1}{6}\)
\(\Rightarrow\left(\frac{3}{4}+\frac{1}{5}\right)\times x=\frac{1}{6}\)
\(\Rightarrow\frac{19}{20}\times x=\frac{1}{6}\)
\(\Rightarrow x=\frac{1}{6}\div\frac{19}{20}\)
\(\Rightarrow x=\frac{10}{57}\)