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a)\(\frac{x}{27}=\frac{-2}{3,6}\)
=>x.3,6=27.(-2)
=>x.3,6=-54
=>x=-15
b)-0,52:x=-9,36:16,38
=>-0,52:x=-4/7
=>x=0,91
c)\(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\)
=>\(2\frac{7}{8}.x=4\frac{1}{4}.1,61\)
=>\(2\frac{7}{8}.x=\frac{2737}{400}\)
=>x=\(\frac{119}{50}\)
a,\(\frac{x}{27}=-\frac{2}{3,6}\)
\(\Leftrightarrow x.3,6=27.-2\)
\(\Leftrightarrow x.3,6=-54\)
\(\Leftrightarrow x=-15\)
b,\(-0,52\div x=-9,36\div16,38\)
\(\Leftrightarrow-0,52\div x=-\frac{4}{7}\)
\(\Leftrightarrow x=\frac{91}{100}\)
c,\(\frac{4\frac{1}{4}}{2\frac{7}{8}}=\frac{x}{1,61}\)
\(\Leftrightarrow\frac{4,25}{2,875}=\frac{x}{1,61}\)
\(\Leftrightarrow x.2,875=4,25.1,61\)
\(\Leftrightarrow x.2,875=6,8425\)
\(\Leftrightarrow x=2,38\)
Lời giải :
Theo đề bài ta có \(\frac{x}{\frac{5}{2}}=\frac{y}{\frac{4}{3}}=\frac{z}{\frac{6}{5}}\Leftrightarrow\frac{2x}{5}=\frac{3y}{4}=\frac{5z}{6}\)
Đặt \(\frac{2x}{5}=\frac{3y}{4}=\frac{5z}{6}=k\)
\(\Leftrightarrow\hept{\begin{cases}x=\frac{5k}{2}\\z=\frac{6k}{5}\end{cases}}\)
Mặt khác : \(\frac{x}{2}=\frac{z-28}{3}\)
\(\Leftrightarrow3x-2z=-56\)
\(\Leftrightarrow3\cdot\frac{5k}{2}-2\cdot\frac{6k}{5}=-56\)
\(\Leftrightarrow k=\frac{-560}{51}\)
\(\Leftrightarrow\hept{\begin{cases}x=\frac{-1400}{51}\\y=\frac{-2240}{153}\\z=\frac{-224}{17}\end{cases}}\)
\(B=x+y-z=\frac{-1400}{51}+\frac{-2240}{153}-\frac{-224}{17}=\frac{-4424}{153}\)
Z; x<21
a.=>x-2<0=>x<2
b.=>3x+6<0=>3x<-6=>x<-2
Chúc bạn học tốt ! ^_^
\(c)\)
\(2x-\frac{1}{2}-\frac{1}{6}-\frac{1}{12}-...-\frac{1}{49.50}=\left(7-\frac{1}{50}+x\right)\)
\(\Rightarrow2x-\left(\frac{1}{2}+\frac{1}{6}+\frac{1}{12}+...+\frac{1}{49.50}\right)=\left(\frac{350}{50}-\frac{1}{50}+x\right)\)
\(\Rightarrow2x-\left(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\right)=\frac{349}{50}+x\)
\(\Rightarrow2x-\left(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\right)-x=\frac{349}{50}\)
\(\Rightarrow x-\left(1-\frac{1}{50}\right)=\frac{349}{50}\)
\(\Rightarrow x-\frac{49}{50}=\frac{349}{50}\)
\(\Rightarrow x=\frac{349}{50}+\frac{49}{50}\)
\(\Rightarrow x=\frac{199}{25}\)
Vậy \(x=\frac{199}{25}\)
~ Ủng hộ nhé
\(a)2.x-3=x+\frac{1}{2}\)
\(\Rightarrow2x-3-x=\frac{1}{2}\)
\(\Rightarrow x-3=\frac{1}{2}\)
\(\Rightarrow x=\frac{1}{2}+3\)
\(\Rightarrow x=\frac{1}{2}+\frac{6}{2}\)
\(\Rightarrow x=\frac{7}{2}\)
Vậy \(x=\frac{7}{2}\)
\(b)4.x-\left(2.x+1\right)=3-\frac{1}{3}+x\)
\(\Rightarrow4.x-2.x-1=\frac{9}{3}-\frac{1}{3}+x\)
\(\Rightarrow2.x-1=\frac{8}{3}+x\)
\(\Rightarrow2x-1-x=\frac{8}{3}\)
\(\Rightarrow x-1=\frac{8}{3}\)
\(\Rightarrow x=\frac{8}{3}+1\)
\(\Rightarrow x=\frac{8}{3}+\frac{3}{3}\)
\(\Rightarrow x=\frac{11}{3}\)
Vậy \(x=\frac{11}{3}\)
~ Ủng hộ nhé