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Dài wa nên mk chỉ ghi đáp án thui nha
a, x=1
b,x=66
c,x=4
d,x=5/3
e,x=17/25
1
\(\left(x-2\right):2.3=6\)
\(\Leftrightarrow\left(x-2\right):2=2\)
\(\Leftrightarrow\left(x-2\right)=4\)
\(\Leftrightarrow x=4+2=6\)
c) ta có
\(\left[\left(2x+1\right)+1\right]m:2=625\)
\(\Leftrightarrow\left[\left(2x+1\right)+1\right]\left\{\left[\left(2x+1\right)-1\right]:2+1\right\}=1250\)
\(\Leftrightarrow\left(2x+1\right)^2+1-1:2+1=1250\)
\(\Leftrightarrow\left(2x+1\right)^2+1-2+1=1250\)
\(\Leftrightarrow\left(2x+1\right)^2+1-2=1249\)
\(\Leftrightarrow\left(2x+1\right)^2+1=1251\)
\(\Leftrightarrow\left(2x+1\right)^2=1250\)
...
2
\(\left(x-\frac{1}{2}\right).\frac{5}{3}=\frac{7}{4}-\frac{1}{2}\)
\(\Leftrightarrow\left(x-\frac{1}{2}\right).\frac{5}{3}=\frac{5}{4}\)
\(\Leftrightarrow\left(x-\frac{1}{2}\right)=\frac{5}{4}:\frac{5}{3}\)
\(\Leftrightarrow\left(x-\frac{1}{2}\right)=\frac{5}{4}.\frac{3}{5}\)
\(\Leftrightarrow x-\frac{1}{2}=\frac{3}{4}\)
\(\Leftrightarrow x=\frac{3}{4}+\frac{1}{2}=\frac{5}{4}\)
\(A=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{2019.2020}\)
\(A=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{2019}-\frac{1}{2020}\)
\(A=1-\frac{1}{2020}\)
\(A=\frac{2019}{2020}\)
\(B=\frac{1}{1.3}+\frac{1}{3.5}+\frac{1}{5.7}+...+\frac{1}{2017.2019}\)
\(2B=\frac{2}{1.3}+\frac{2}{3.5}=\frac{2}{5.7}+...+\frac{2}{2017.2019}\)
\(2B=1-\frac{1}{3}+\frac{1}{3}-\frac{1}{5}=\frac{1}{5}-\frac{1}{7}+...+\frac{1}{2017}-\frac{1}{2019}\)
\(2B=1-\frac{1}{2019}\)
\(2B=\frac{2018}{2019}\)
\(B=\frac{2018}{2019}:2=\frac{1009}{2019}\)
a) \(-\frac{5}{2}:\left(\frac{3}{4}-\frac{1}{2}\right)\)
= \(-\frac{5}{2}:\left(\frac{6}{8}-\frac{4}{8}\right)\)
= \(-\frac{5}{2}:\frac{2}{8}\)
=\(-\frac{5}{2}.\frac{8}{2}\)
=\(-\frac{40}{4}\)
=\(-10\)
b) \(2,8:\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\)
=> \(\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\)
=> \(\left(\frac{1}{5}-3x\right)=\frac{14}{5}:\frac{7}{5}\)
=> \(\left(\frac{1}{5}-3x\right)=\frac{14}{5}.\frac{5}{7}\)
=> \(\frac{1}{5}-3x=2\)
=> \(3x=\frac{1}{5}-2\)
=> \(3x=-\frac{9}{5}\)
=> \(x=-\frac{9}{5}:3\)
=> \(x=-\frac{3}{5}\)
a) \(\frac{-5}{2}:\left(\frac{3}{4}-\frac{1}{2}\right)\\ =\frac{-5}{2}:\left(\frac{3}{4}-\frac{2}{4}\right)\\ =\frac{-5}{2}:\frac{1}{4}\\ =\frac{-5}{2}\cdot4=-10\)
b) \(2,8:\left(\frac{1}{5}-3x\right)=1\frac{2}{5}\\ \Rightarrow\frac{14}{5}:\left(\frac{1}{5}-3x\right)=\frac{7}{5}\\ \Rightarrow\frac{1}{5}-3x=\frac{14}{5}:\frac{7}{5}\\ \Rightarrow\frac{1}{5}-3x=\frac{14}{5}\cdot\frac{5}{7}\\ \Rightarrow\frac{1}{5}-3x=2\\ \Rightarrow3x=\frac{1}{5}-2\\ \Rightarrow3x=\frac{-9}{5}\\ \Rightarrow x=\frac{-9}{5}:3\\ \Rightarrow x=\frac{-9}{5\cdot3}=\frac{-3}{5}\)
Vậy \(x=\frac{-3}{5}\)