a) 2x(x² - xy³)
= 2x.x² - 2x.xy³
= 2x³ - 2x²y³
b) (12x³y⁵ - 21x⁴y²) : 3x²y²
= 12x³y⁵ : 3x²y² - 21x⁴y² : 3x²y²
= 4xy³ - 7x²
a, 2\(x\).(\(x^2\) - \(xy^3\))
= 2\(x^3\) - 2\(x^2\)y3
b, (12\(x^3\)y5 - 21\(x^4\)y2) :(3\(x^2\)y2)
= 3\(x^2\).y2.(4\(xy^3\) - 7\(x^2\))
= 4\(xy^3\) - 7\(x^2\)