a:
=> \(\dfrac{x-3}{5}=\dfrac{18-1+2x}{3}=\dfrac{2x+17}{3}\)
=>5(2x+17)=3(x-3)
=>10x+85=3x-9
=>7x=-94
=>x=-94/7
b: \(\Leftrightarrow\dfrac{15\cdot\left(x-3\right)}{20}+\dfrac{2\left(4x-10.5\right)}{20}=\dfrac{12\left(x+1\right)}{20}+\dfrac{120}{20}\)
=>15(x-3)+2(4x-10,5)=12(x+1)+20
=>15x-45+8x-21=12x+32
=>23x-66=12x+32
=>11x=98
=>x=98/11
c:
ĐKXĐ: x<>1; x<>-1
\(\dfrac{3}{1+x}+\dfrac{2}{x-1}=\dfrac{5x}{1-x^2}\)
=>\(\dfrac{3\left(x-1\right)+2\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{-5x}{x^2-1}\)
=>3x-3+2x+2=-5x
=>5x-1=-5x
=>10x=1
=>x=1/10(nhận)
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