Bài 2:
a: \(\dfrac{15x^3y^4-10x^2y^4+5xy^3}{-5xy^2}\)
\(=-3x^2y^2+2xy^2-y\)
b: \(\left[7\left(2x-5y\right)\left(2x+5y\right)-2\left(14x^2-3y^2\right)\right]:\left(-3y\right)\)
\(=\left[7\left(4x^2-25y^2\right)-2\left(14x^2-3y^2\right)\right]:\left(-3y\right)\)
\(=\left(28x^2-175y^2-28x^2+6y^2\right):\left(-3y\right)\)
\(=171y^2:3y=57y\)