计算:(1)2x 2 y•(-3xy)÷(xy) 2 (2)(-2a)•(3a 2 -a+3)(3)(x+3)(x+4)
1个回答

(1)原式=2x 2y•(-3xy)÷x 2y 2=-6x 3y 2÷x 2y 2=-6x;

(2)原式=-2a•3a 2-(-2a)•a+(-2a)×3=-6a 3+2a 2-6a;

(3)原式=x 2+4x+3x+12-(x 2-2x+1)=x 2+4x+3x+12-x 2+2x-1=9x+11;

(4)原式=(x 2-9)(x 2-9)=x 4-81;

(5)原式=(2a 4x 2-4a 3x 3-

3

4 a 2x 2)÷a 2x 2=2a 2-4ax-

3

4 .