4.a^3-5a+45.(x-y)^2+3(x^2-y^2)-4(x+y)^26.2m^2(n+2)-12mn-3n^2
热心网友
4.a^3-5a+4=(a－1)(a－4)5.(x-y)^2+3(x^2-y^2)-4(x+y)^2=(x－y＋4x＋4y)(x－y－x－y)=－2y(5x＋3y)6.2m^2(n+2)-12mn-3n^2（m－3） =2m^2n＋4m^2－12mn－3mn^2＋9n^2=mn(2m－3n)＋(2m－3n)^2=(2m－3n)(mn＋2m－3n)
热心网友
是因式分解?4.a^3-5a+4=a^3-1-(5a-5)=(a-1)(a^2+a+1)-5(a-1)=(a-1)(a^2+a-4)拆项分解法5.(x-y)^2+3(x^2-y^2)-4(x+y)^2(十字相乘法)=［(x-y)+4(x+y)］［(x-y)-(x+y)］=-2y(5x+3y)6.2m^2(n+2)-12mn-3n^2 题目有问题