1.C 2.C 3.C 4.C 5.D
6.x²+ xy -6y²
7.x² +x-2
8.9a²-b²
9.x³-y³
10.(x²+ax+bx)
11.2/3
12.解:
(1)原式=x³+1
(2)原式=2x³-8x² -x +4 - 2x³+5x² -6x +15= -3x² -7x +19
(3)原式=x² -6x+8 -x²+4x-3= -2x+5
13.解:原式=x³+x²-2x+3x³-12x²+6x=4x³-11x²+4x
当x=1/2时,原式=4×(1/2)³-11×(1/2)²+4×(1/2)=1/2-11/4+2=-1/4.
14.解:∵x²-x+15=x²+5x+4,∴6x=11,x=11/6.
15.解:梯形的面积为1/2[(4n+3m)+(2m+5n)](m+2n)=(1/2)(5m+9n)(m+2n)=(5/2m²+19/2mn+9n²)(cm²).
16.解:阴影部分的面积为(3a+2b)(3a+6)-3a(b+2)=9a²+6ab+2b²-6a.
17.解:a² +5a +6 a²-a -6 a²+a -6 a²-5a +6
(1)x²+(m+n)x+mn
(2)x² +8x -4016000
19解:4x²-4x -8 >4x²+4x -24 -8 x> -16 x<2 所以,x取0,1