You group the like terms and multiply, and remember that when you multiply two like terms like x^4 times x^3 you ADD the exponents, so you would have x^7. For this problem: so for the x's: -3x^2(4x^3) = -12x^5; now for the y's: y^2(y^4) = y^6; so your final answer is -12x^5y^6
