a) \(5x^2.(3x^2 – 7x + 2)\)
\(= 5x^2.3x^2 - 5x^2.7x + 5x^2.2\)
\(= 15x^4 - 35x^3 + 10x^2\)
b) \(\dfrac{2}{3}xy.(2x^2y - 3xy + y^2)\)
\(= \dfrac{2}{3}xy.2x^2y - \dfrac{2}{3}xy.3xy + \dfrac{2}{3}xy.y^2\)
\(= \dfrac{4}{3}x^3y^2 - 2x^2y^2 + \dfrac{2}{3}xy^3\)
Lưu ý: \(\text{Với} \, a \ne 0,\, a^m.a^n = a^{m + n}\)
