\(x=-280\)
 

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

\(\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\)

\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}=\frac{5}{3}\left(x\ne12,x\ne0\right)\)

\(\Leftrightarrow\frac{240}{x-12}-\frac{240}{x}-\frac{5}{3}=0\)

\(\Leftrightarrow\frac{720x-720x+8640-5x^2+60x}{3x\left(x-12\right)}=0\)

\(\Leftrightarrow8640-5x^2+60x=0\)

\(\Leftrightarrow5\left(1728-x^2+12x\right)=0\)

\(\Leftrightarrow5\left(-x^2+12x+1728\right)=0\)

\(\Leftrightarrow5\left(-x^2+48x-36x+1728\right)=0\)

\(\Leftrightarrow5\left[-x\left(x-48\right)-36\left(x-48\right)\right]=0\)

\(\Leftrightarrow5\left[-\left(x-48\right)\right].\left(x+36\right)=0\)

\(\Leftrightarrow-5\left(x-48\right).\left(x+36\right)=0\)

\(\Leftrightarrow\left(x-48\right)\left(x+36\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x-48=0\\x+36=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.,x\ne12,x\ne0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=48\\x=-36\end{matrix}\right.\)

\(5x-200=\frac{5x}{2}-300+2x+300\)0 

 \(3x-2,5x=200\)\(0,5x=200\)\(x=400\)

\(\frac{x+10}{90}+\frac{x+20}{80}+\frac{x+30}{70}+\frac{x+40}{60}+\frac{x+50}{50}=-5\)

<=> \(\frac{x+10}{90}+1+\frac{x+20}{80}+1+\frac{x+30}{70}+1+\frac{x+40}{60}+1+\frac{x+50}{50}+1=0\)

<=> \(\frac{x+100}{90}+\frac{x+100}{80}+\frac{x+100}{70}+\frac{x+100}{60}+\frac{x+100}{50}=0\)

<=> \(\left(x+100\right)\left(\frac{1}{90}+\frac{1}{80}+\frac{1}{70}+\frac{1}{60}+\frac{1}{50}\right)=0\)

<=> x + 100 = 0 

<=> x = -100

Vậy x = -100

sai đề bài rồi bạn ơi

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 @@@

\(=>71+300=\frac{x}{x}+\frac{120}{x}+240\)

\(=>371=1+\frac{120}{x}+240\)

\(=>371=\frac{120}{x}+241\)

\(=>\frac{120}{x}=371-241\)

\(=>\frac{120}{x}=120\)

=>x=120:120

=>x=1

\(\Leftrightarrow\frac{x+10}{270}+1+\frac{x+20}{260}+1=\frac{x+30}{250}+1+\frac{x+40}{240}+1\)

\(\Leftrightarrow\frac{x+280}{270}+\frac{x+280}{260}=\frac{x+280}{250}+\frac{x+280}{240}\)

\(\Leftrightarrow\left(x+280\right)\left(\frac{1}{270}+\frac{1}{260}\right)=\left(x+280\right)\left(\frac{1}{250}+\frac{1}{240}\right)\)

\(\Leftrightarrow\left(x+280\right)\left(\frac{1}{270}+\frac{1}{260}-\frac{1}{250}-\frac{1}{240}\right)=0\)

=>x=-280

đề vế phải sai rồi