- 4x^2y * 3xy^3
multiply the numbers : 4*3 = 12
-12x^2xy^3y
apply exponent rule : x^2x = x^2+1 = x^3
-12x^3y^3y
apply exponent rule again : y^3y = y^1+3 = y^4
answer : -12x^3y^4
