Answer:
x⁴ +2x³ + x² + 12x
Step-by-step explanation:
(x² + 3x)(x² - x +4)
= x²(x²) - x(x²) + 4(x²) + x²(3x) - x(3x) + 4(3x)
= x^4 - x³ + 4x² + 3x³-3x²+12x
= x⁴ +2x³ + x² + 12x
