Bài 3:
a: \(\dfrac{5x^2+10xy+5y^2}{3x^3+3y^3}=\dfrac{5\left(x+y\right)^2}{3\left(x+y\right)\left(x^2-xy+y^2\right)}=\dfrac{5\left(x+y\right)}{3\left(x^2-xy+y^2\right)}\)
b: \(3x\left(2x-1\right)-\left(2x+1\right)\left(3x+2\right)\)
\(=6x^2-3x-6x^2-4x-3x-2\)
=-10x-2