1: ĐKXĐ:  \(x\notin\left\{0;3\right\}\)

\(\dfrac{x+3}{x}-\dfrac{x}{x-3}+\dfrac{9}{x^2-3x}\)

\(=\dfrac{x+3}{x}-\dfrac{x}{x-3}+\dfrac{9}{x\left(x-3\right)}\)

\(=\dfrac{\left(x+3\right)\left(x-3\right)-x^2+9}{x\left(x-3\right)}\)

\(=\dfrac{x^2-9-x^2+9}{x\left(x-3\right)}\)

=0

2: ĐKXĐ: \(x\notin\left\{0;1\right\}\)

\(\dfrac{3}{x}-\dfrac{5}{x-1}+\dfrac{3x+2}{x^2-x}\)

\(=\dfrac{3}{x}-\dfrac{5}{x-1}+\dfrac{3x+2}{x\left(x-1\right)}\)

\(=\dfrac{3x-3-5x+3x+2}{x\left(x-1\right)}\)

\(=\dfrac{x-1}{x\left(x-1\right)}=\dfrac{1}{x}\)

Giúp mk câu hỏi này vs

\(2x\left(3x^2-7x+2\right)\)

\(=6x^3-14x^2+4x\)

\(\left(x-2\right)\left(3x^2+2x+4\right)\)

\(=3x^3+\left(-4x^2\right)+\left(-8\right)\)

\(\left(3x^2y^2+6x^2y^3-12xy\right)\div3xy\)

\(=xy+2xy-4\)

x^2/x-2+4-4x/x-2 ???

\(=\dfrac{6x^3+3x^2-10x^2-5x+4x+2}{2x+1}=3x^2-5x+2\)

\(\dfrac{5x+5y}{3x-3y}:\dfrac{5x}{x^2-y^2}.\)

\(=\dfrac{5\left(x+y\right)}{3\left(x-y\right)}.\dfrac{\left(x-y\right)\left(x+y\right)}{5x}.\)

\(=\dfrac{x+y}{3}.\dfrac{x+y}{x}.\)

\(=\dfrac{\left(x+y\right)^2}{3x}.\)

Cảm ơn nha

\(\dfrac{2x^2-x}{x-1}+\dfrac{x+1}{1-x}+\dfrac{2-x^2}{x-1}.\left(x\ne1\right).\)

\(\dfrac{2x^2-x-x-1+2-x^2}{x-1}=\dfrac{x^2-2x+1}{x-1}=\dfrac{\left(x-1\right)^2}{x-1}=x-1.\)

a: \(=-\left(10x^2+15x-8x-12\right)=-10x^2-7x+12\)

-10x^2-7x+12