(\(\frac{x}{40}\)+\(\frac{240-x}{60}\)) + (\(\frac{x}{45}\)+\(\frac{240-x}{50}\)) = 0,25
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HD dùng PP Quy đồng tử (không quy đồng Mẫu)
\(\left(\frac{x+10}{270}+10\right)+\left(\frac{x+20}{260}+10\right)=\left(\frac{x+30}{250}+10\right)+\left(\frac{x+40}{240}+10\right)\\ \)
\(\left(x+280\right)\left(....\right)=0\)chú ý (...) thường khác không nếu bằng =0=> đúng với mọi x
nếu khác không=> x=-280
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\)
\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\left(x\ne12,x\ne0\right)\)
\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}-\frac{5}{3}=0\)
\(\Leftrightarrow\frac{720x-720x+8640-5x^2+60x}{3x\left(x-12\right)}=0\)
\(\Leftrightarrow8640-5x^2+60x=0\)
\(\Leftrightarrow5\left(1728-x^2+12x\right)=0\)
\(\Leftrightarrow5\left(-x^2+12x+1728\right)=0\)
\(\Leftrightarrow5\left(-x^2+48x-36x+1728\right)=0\)
\(\Leftrightarrow5\left[-x\left(x-48\right)-36\left(x-48\right)\right]=0\)
\(\Leftrightarrow5\left[-\left(x-48\right)\right].\left(x+36\right)=0\)
\(\Leftrightarrow-5\left(x-48\right).\left(x+36\right)=0\)
\(\Leftrightarrow\left(x-48\right)\left(x+36\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-48=0\\x+36=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.,x\ne12,x\ne0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(5x-200=\frac{5x}{2}-300+2x+300\)0
\(3x-2,5x=200\)\(0,5x=200\)\(x=400\)
![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)
<=> \(\frac{x+10}{90}+1+\frac{x+20}{80}+1+\frac{x+30}{70}+1+\frac{x+40}{60}+1+\frac{x+50}{50}+1=0\)
<=> \(\frac{x+100}{90}+\frac{x+100}{80}+\frac{x+100}{70}+\frac{x+100}{60}+\frac{x+100}{50}=0\)
<=> \(\left(x+100\right)\left(\frac{1}{90}+\frac{1}{80}+\frac{1}{70}+\frac{1}{60}+\frac{1}{50}\right)=0\)
<=> x + 100 = 0
<=> x = -100
Vậy x = -100
![](https://rs.olm.vn/images/avt/0.png?1311)
ko chép lại đầu bài nha
=(53x+800):7020=(49x+147):6000
=(53x+800).6000=70
x=145,0369515
lưu ý:mik làm theo cách suy luận nhé @@@
![](https://rs.olm.vn/images/avt/0.png?1311)
\(=>71+300=\frac{x}{x}+\frac{120}{x}+240\)
\(=>371=1+\frac{120}{x}+240\)
\(=>371=\frac{120}{x}+241\)
\(=>\frac{120}{x}=371-241\)
\(=>\frac{120}{x}=120\)
=>x=120:120
=>x=1
tìm x giúp m nha đúng mình tíck
\(\frac{x+10}{270}+\frac{x+20}{260}=\frac{x+3}{250}+\frac{x+3}{240}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\Leftrightarrow\frac{x+10}{270}+1+\frac{x+20}{260}+1=\frac{x+30}{250}+1+\frac{x+40}{240}+1\)
\(\Leftrightarrow\frac{x+280}{270}+\frac{x+280}{260}=\frac{x+280}{250}+\frac{x+280}{240}\)
\(\Leftrightarrow\left(x+280\right)\left(\frac{1}{270}+\frac{1}{260}\right)=\left(x+280\right)\left(\frac{1}{250}+\frac{1}{240}\right)\)
\(\Leftrightarrow\left(x+280\right)\left(\frac{1}{270}+\frac{1}{260}-\frac{1}{250}-\frac{1}{240}\right)=0\)
=>x=-280