(2x+3y)(x-4y)、(5x-y)(-x-3y)、(3-x)(4+y)谁告诉我这类题怎么做呀?

(2x+3y)(x-4y)、(5x-y)(-x-3y)、(3-x)(4+y)谁告诉我这类题怎么做呀? 5x+6y+3x-4y+3-x+x =5x+3x-x+x+6y-4y+3 =8x=2y+3 谁能告诉我这题合并同类项的解 (2x-3y)2-(4y-3x)(3x+4y)怎么做? [(3x+y)²-(3x-y)²]÷(4x-2y)计算 怎么做? （x+2)(x+3) (x-4)(x+1) (y+4)(y-2) (y-5)(y-3) 3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27 (x+3y-4)(2x-y) 计算(x^8-x^7y+x^5y^3-x^4y^4+x^3y^5-x^y^7+y^8)(x^2+xy+y^2) x^8-x^7y+x^6y^2-x^5y^3+x^4y^4-x^3y^5+x^2y^-xy^7+y^8 (y-x)(x-y)^3(y-x)^5怎么算 x/x-y*y^2/x+y-x^3y2/x^4-y^4/x^2/x^2+y^2 有这样一道题:"计算(2*x*x*x-3*x*x*y-2*x*y*y)-(x*x*x-2*x*y*y+y*y*y)+【-