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\(D=\frac{5}{1+2+3}+\frac{5}{1+2+3+4}+...+\frac{5}{1+2+...+100}\)
\(\Rightarrow D=5\left(\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+...+\frac{1}{1+2+...+100}\right)\)
\(\Rightarrow D=5\left(\frac{1}{\frac{4.3}{2}}+\frac{1}{\frac{5.4}{2}}+...+\frac{1}{\frac{101.100}{2}}\right)\)
\(\Rightarrow D=5\left(\frac{2}{3.4}+\frac{2}{4.5}+...+\frac{2}{100.101}\right)\)
\(\Rightarrow D=10\left(\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{100}-\frac{1}{101}\right)\)
\(\Rightarrow D=10\left(\frac{1}{3}-\frac{1}{101}\right)\)
\(\Rightarrow D=\frac{10}{3}-\frac{10}{101}=\frac{980}{303}\)
I don't now
or no I don't
..................
sorry
\(A=\frac{1}{1+2}+\frac{1}{1+2+3}+\frac{1}{1+2+3+4}+\frac{1}{1+2+3+4+5}\)
\(A=\frac{1}{\left(1+2\right).2:2}+\frac{1}{\left(1+3\right).3:2}+\frac{1}{\left(1+4\right).4:2}+\frac{1}{\left(1+5\right).5:2}\)
\(A=\frac{2}{2.3}+\frac{2}{3.4}+\frac{2}{4.5}+\frac{2}{5.6}\)
\(A=2\left(\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+\frac{1}{5}-\frac{1}{6}\right)\)
\(A=2\left(\frac{1}{2}-\frac{1}{6}\right)\)
\(A=2.\frac{1}{3}=\frac{2}{3}\)
biểu thức 1:
\(c1:\frac{3}{4}:\frac{2}{3}+\frac{1}{4}:\frac{2}{3}=\left(\frac{3}{4}+\frac{1}{4}\right):\frac{2}{3}=1:\frac{2}{3}=\frac{3}{2}\)
\(c2=\frac{3}{4}:\frac{2}{3}+\frac{1}{4}:\frac{2}{3}=\frac{9}{8}+\frac{3}{8}=\frac{3}{2}\)
biểu thức 2:
\(c1:\left(2,07+2,13\right):0,15=4,2:0,15=28\)
\(c2:\left(2,07+2,13\right):0,15=2,07:0,15+2,13:0,15=13,8+14,2=28\)
C1:\(=\frac{3}{4}x\frac{3}{2}+\frac{1}{4}x\frac{3}{2}\)
\(=\frac{9}{8}+\frac{3}{8}\)
\(=\frac{12}{8}\)
\(=\frac{3}{2}\)
C2:\(=\left(\frac{3}{4}+\frac{1}{4}\right)x\frac{3}{2}\)
\(=1x\frac{3}{2}\)
\(=\frac{3}{2}\)
\(x=\)nhân nha bn!
https://olm.vn/hoi-dap/question/893332.html
câu trả lời đó
mk thấy nó cx giống vs bài của cậu
hok tốt
`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`.
