Rút gọn biểu thức: (3x^2-5xy- 4y^2) . ( 2x^2+ y^2) + ( 2x^4y- x^3y^3- x^2y^4) :( 1/5xy) .

3x2−5xy−4y2   .  2x2+y2+2x4y−x3y3−x2y4:15xy

= 6x⁴ – 10x³y – 8x²y² + 3x²y² – 5xy³ – 4y⁴ + 10x³ – 5x²y² – 5xy³

= 6x⁴ – 10x³y + (3x²y² – 8x²y² – 5x²y²) – (5xy³ + 5xy³) – 4y⁴ + 10x³

= 6x⁴ – 10x³y + (3x²y² – 8x²y² – 5x²y²) – (5xy³ + 5xy³) – 4y⁴ + 10x³

= 6x⁴ – 10x³y – 10x²y² – 10xy³ – 4y⁴ + 10x³.