Bài 1: \(=\dfrac{2}{3}a^6b^3-a^4b^5\)
Bài 2:
\(a,=m^2+10m+25\\ b,=\left(5x-7\right)\left(5x+7\right)\\ c,=\dfrac{1}{8}m^3-\dfrac{1}{2}m^2n+mn^2-\dfrac{8}{27}n^3\\ d,=\left(\dfrac{1}{2}x-3\right)\left(\dfrac{1}{4}x^2+\dfrac{3}{2}x+9\right)\)
Bài 3:
\(\Leftrightarrow3x^2-3x+2x-2-3\left(x^2-x-2\right)=4\\ \Leftrightarrow3x^2-x-3x^2+3x+6=6\\ \Leftrightarrow2x=0\Leftrightarrow x=0\)