12x^2y*(-2/3x^2-5/6xy+3/4y^2)能告诉一下解决这类题的技巧吗?

[2(x-y)^5-8(x-y)^2(x+y)+6y(x-y)^2]÷2(x-y)^2[2(x-y)^3-8(x-y)^2(x+y)+6y(x-y)^2]÷2(x-y)^2 因式分解3x^2(x-y)+6x(y-x) 化简(x+y)-(2x+y/2)-(3x+y/6)-(4x+y/12)-(5x+y/20)-……-(10x+y/90) (1)x^2*x^8+x^13/x^3 (2)a^19/a^12/a^3 (3) (x-2y)^5/(2y-x)^3 (4)(x-y)^5/(x-y) (5)(x-y)^6/(y-x)^4 2(2x+3y)(3x+2y)-(6x-y)(2x-5y) x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2 [12(x+y)^3+3(x+y)(x-y)^2]÷6(x+y) 因式分解x次方-y次方+5x-y+6【x-y+2】【x+y+3】 6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5 1.) 5/x-x+12-2x/2x-2x 2)y/2x-2y/3x 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 x(x-y)2-(y-x)3 1.(x^3-x^2-4x+1)/(x^2-3x+2)-(x^3-2x^2-9x+21)/（x^2-5x+6）+（x^2-3x+8）/（x^2-4x+3）2.{(x^2)/（x-y)}*{y/(x+y)}-{(x^4y)/(x^4-y^4)}÷{（x^2/x^2+y^2）^2} *-----------------------------------------------*| 6 4 X | 8 X X | X X 5 || X X X | X X X | X 7 8 || X X X | X X X | X X X ||---------------+---------------+--------------- || X X X | X X X | 5 1 X || X X X | X 6 X | X X X || 8 X X | 3 5 X | 2 X X || 化简:5(x-y)+2(x+y)-3(x-y) [2/3x-2/x+y(x+y/3x-x-y)]/x-y/x 化简：{2/3x-2/(x+y)[(x+y)/3x-x-y]}/(x+y)/x 计算2/3x-2/x+y(x+y/3x-x-y)/x-y/x