1、(3ab-2a)÷a =a(3b-2)/a=3b-2
2、（x^3-2x^y)÷(-x^2)= x-2y
3、-21a^2b^3÷7a^2b =-3b^2
4、(6a^3b-9a^c)÷3a^2 =3a^2(2ab-3c)/3a^2=2ab-3c
5、(5ax^2+15x)÷5x=5x(a+3x)÷5x =a+3x
6、(a+2b)(a-2b)=a^2-4b^2
7、(3a+b)^2=9a^2+b^2 +12ab
8、(1/2 a-1/3 b)^2 =1/4a^2+1/9b^2-1/18ab
9、(x+5y)(x-7y)=x^2-7x+5x-35y^2=x^2-2x-35y^2
10、(2a+3b)(2a+3b)4a^2+9b^2 ++12ab
11、(x+5)(x-7)=x^2-7x+5x-35=x^2-2x-35
12、5x^3×8x^2 =40x^5
13、-3x×(2x^2-x+4)=-6x^3+3x^2-12x
14、11x^12×(-12x^11)=-132 x^23
15、(x+5)(x+6)=x^2+11x+30
16、(2x+1)(2x+3)=4x^2+6x+2x+4=4x^2+8x+4
17、3x^3y×(2x^2y-3xy)=6x^5y^2-9x4y^2
18、2x×(3x^2-xy+y^2)=6x^3-2x^2y+2xy^2
19、(a^3)^3÷(a^4)^2=a^9/a^8=a
20、(x^2y)^5÷(x^2y)^3 =x^2y)^2
(x+y)^4 -13(x+y)^2 +36
=[(x+y)^2-4][(x+y)^2-9]
=(x+y+2)*(x+y-2)(x+y+3)*(x+y-3)
30、x^3-25x=x(x^2-25)
31、x^3+4x^2+4x=x(x+2)^2
32、(x+2)(x+6)=x^2+8x+12
33、2a×3a^2=6a^3
34、(-2mn^2)^3=-8m^3*n^6
35、（-m+n)(m-n）=-m^2+2mn-n^2
36、27x^8÷3x^4=9x^4
37、(-2x^2)×(-y)+3xy×(1-1/3 x)=2x^2*y+3xy-x^2*y=x^2*y+3xy
38、am-an+ap=a(m-n+p)
39、25x^2+20xy+4y^2=(5x+2y)^2
40、(-4m^4+20m^3n-m^2n^2)÷(-4m^2)=m^2-5mn-1/4n^2
41、(12p^3q^4+20p^3q^2r-6p^4q^3)÷(-2pq)^2=3pq^2+5pr-3/2p^2*q
42、[4y(2x-y)-2x(2x-y)]÷(2x-y)=4y-2x
43、(x^2y^3-1/2 x^3y^2+2x^2y^2)÷1/2 xy^2=2xy-x^2+4x
44、(4a^3b^3-6a^2b^3c-2ab^5)÷(-2ab^2)=-2a^2*b+3abc+b^3
45、（ax+bx)÷x=a+b
46、(ma+mb+mc)÷m=a+b+c
47、(9x^4-15x^2+6x)÷3x=3x^3-5x+2
48、(28a^3b^2c+a^2b^3-14a^2b^2)÷(-7a^2b)=-4abc-1/7b^2+2b
49、(6xy^2)^2÷3xy=12xy ^3
50、24a^3b^2÷3ab^2=8a^2