1.(6×108)(7×109)(4×104)．
2.(-5xn+1y)•(-2x)．
3.(-3ab)•(-a2c)•6ab2．
4.(-4a)•(2a2+3a-1)．
5.(3m-n)(m-2n)．
6.(x+2y)(5a+3b)．
7.(-ab)3•(-a2b)•(-a2b4c)2．
8.[(-a)2m]3•a3m+[(-a)5m]2．
9.xn+1(xn-xn-1+x)．
10.(x+y)(x2-xy+y2)．
11.5x(x2+2x+1)-(2x+3)(x-5)．
12.(2x-3)(x+4)．
13.(-2ambn)(-a2bn)(-3ab2)．
14.(m-n)(m5+m4n+m3n2+m2n3+mn4+n5)．
15.(2a2-1)(a-4)(a2+3)(2a-5)．
16.2[(x+2)(x+1)-3]+(x-1)(x-2)-3x(x+3)．
17.(0.3a3b4)2•(-0.2a4b3)3．
18.(-4xy3)•(-xy)+(-3xy2)2．
19.(5a3+2a-a2-3)(2-a+4a2)．
20.(3x4-2x2+x-3)(4x3-x2+5)．
21.(3am+2bn+2)(2am+2am-2bn-2+3bn)．
22.[(-a2b)3]3•(-ab2)．
23.(-2ab2)3•(3a2b-2ab-4b2)．
24.(-2xmyn)3•(-x2yn)•(-3xy2)2．
25.(0.2a-1.5b+1)(0.4a-4b-0.5)．
26.-8(a-b)3•3(b-a)．
27.(x+3y+4)(2x-y)．
28.y[y-3(x-z)]+y[3z-(y-3x)]．
29.计算[(-a)2m]3•a3m+[(-a)3m]3(m为自然数)．
30.(x-x2-1)(x2-x+1)n(x-x2-1)2n
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