Diện tích sân chơi là \(12\cdot20=240\left(m^2\right)\)

Số tấm cỏ là \(240:0,5^2=960\)

Số tiền là \(960\cdot20000=19200000\left(đồng\right)\)

\(\dfrac{x+3}{x}-\dfrac{x}{x-3}+\dfrac{9}{x^2-3x}=\dfrac{x^2-9-x^2+9}{x\left(x-3\right)}=\dfrac{0}{x\left(x-3\right)}=0\)

\(\Leftrightarrow-3\left(x+3\right)=4\left(2x-1\right)\left(x\ne-3\right)\\ \Leftrightarrow-3x-9=8x-4\\ \Leftrightarrow11x=-5\Leftrightarrow x=-\dfrac{5}{11}\left(tm\right)\)

\(a,=10x^3-5x^2+5x\\ b,=x^3+27\\ c,=\dfrac{5}{2}xy-1-\dfrac{1}{2}y\\ d,=\left(2x^3-10x^2-11x^2+55x+12x-60\right):\left(x-5\right)\\ =\left[2x^2\left(x-5\right)-11x\left(x-5\right)+12\left(x-5\right)\right]:\left(x-5\right)\\ =2x^2-11x+12\)

\(a,B=\dfrac{3}{3+2}=\dfrac{3}{5}\\ b,P=A+B=\dfrac{2x+3x^2-3x^2-6x+2x-x^2}{\left(2-x\right)\left(2+x\right)}=\dfrac{-x\left(x+2\right)}{\left(2-x\right)\left(2+x\right)}=\dfrac{x}{x-2}\\ c,P=\dfrac{x-2+2}{x-2}=1+\dfrac{2}{x-2}\in Z\\ \Leftrightarrow x-2\inƯ\left(2\right)=\left\{-2;-1;1;2\right\}\\ \Leftrightarrow x\in\left\{0;1;3;4\right\}\left(tm\right)\)

\(a,=4x^2-4x-3-4x^2=-4x-3\\ b,=x^2-4xy+4y^2-x^2+4xy=4y^2\\ c,=x^3-3x^2y+3xy^2-y^3+y^3+3x^2y-3xy^2=x^3\\ d,=\dfrac{x^2+x+x^2+x}{\left(x-1\right)\left(x+1\right)}=\dfrac{2x\left(x+1\right)}{\left(x-1\right)\left(x+1\right)}=\dfrac{2x}{x-1}\)

\(a,=4x^2+4xy+y^2\\ b,=9x^2-12xy+4y^2\\ c,=x^4-\dfrac{4}{9}y^2\\ d,=x^3-8y^3\\ e,=8x^3+12x^2y^2+6xy^4+y^6\\ f,=27x^6-54x^4y+36x^2y^2-8y^3\\ g,=\left(x^2-1\right)\left(x^2+1\right)=\left(x-1\right)\left(x+1\right)\left(x^2+1\right)\\ h,=\left(4x^2-y^2\right)\left(4x^4+2x^2y^2+y^4\right)=\left(2x-y\right)\left(2x+y\right)\left(4x^4+2x^2y^2+y^4\right)\)

\(a,\Leftrightarrow2x^2-x-2x^2-2=0\\ \Leftrightarrow-x-2=0\Leftrightarrow x=-2\\ b,\Leftrightarrow x\left(3x-2\right)=0\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{2}{3}\end{matrix}\right.\\ c,\Leftrightarrow x^2\left(x+1\right)-4\left(x+1\right)=0\\ \Leftrightarrow\left(x-2\right)\left(x+2\right)\left(x+1\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=2\\x=-2\\x=-1\end{matrix}\right.\)

Đề sai rồi b

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