\(A=\frac{1}{2.4}\)+\(\frac{1}{4.6}\)\(+\)\(\frac{1}{6.8}\)\(+\)\(\frac{1}{8.10}\)\(+\)\(\frac{1}{10.12}\)\(+\)\(\frac{1}{12.14}\)
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LT
1
NH
3
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I
19 tháng 2 2020
a) 178-5(x+1)=78
=> 5(x+1)=100
=>x+1 = 20
=> x =19
b) 3x +17 =2
=>3x = -15
=> x= -5
c) -5x + 17 =-19
=> -5x = -36
=> x= 36/5
CHúc bạn học tốt . Kick cho mk nha @@
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NV
0
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=>2A=2(1/2x4+1/4.6+1/6.8+1/8.10+1/10.12+1/12.14)
=> 2A=2/2.4 + 2/4.6 + 2/6.8 + 2/8.10 + 2/10.12 + 2/12.14
=> 2a =1 - 1/2 + 1/2 - 1/3 + 1/3 - 1/4 + 1/4 - 1/5 + 1/5 - 1/6 + 1/6 - 1/7
=> 2A =1-1/7
=>2A=16/17
=> A= 8/17
Mình chắc chắn . Chúc bạn học tốt
\(A=\frac{1}{2.4}\)\(+\frac{1}{4.6}\)\(+\frac{1}{6.8}\)\(+\frac{1}{8.10}\)\(+\frac{1}{10.12}\)\(+\frac{1}{12.14}\)
\(\Rightarrow2A=2.\left(\frac{1}{2.4}+\frac{1}{4.6}+\frac{1}{6.8}+\frac{1}{8.10}+\frac{1}{10.12}+\frac{1}{12.14}\right)\)
\(\Rightarrow2A=\frac{2}{2.4}+\frac{2}{4.6}+\frac{2}{6.8}+\frac{2}{8.10}+\frac{2}{10.12}+\frac{2}{12.14}\)
\(\Rightarrow2A=\frac{1}{2}-\frac{1}{4}+\frac{1}{4}-\frac{1}{6}+\frac{1}{6}-\frac{1}{8}+\frac{1}{8}-\frac{1}{10}+\frac{1}{10}-\frac{1}{12}+\frac{1}{12}-\frac{1}{14}\)
\(\Rightarrow2A=\frac{1}{2}-\frac{1}{14}=\frac{7}{14}-\frac{1}{14}=\frac{6}{14}\)
\(\Rightarrow2A=\frac{6}{14}\)
\(\Rightarrow A=\frac{3}{14}\)