三道代数计算题

题目

三道代数计算题
⑴6x2-5xy-6y2-2xz-23yz-20z2
⑵x3+6x2+12x+9
⑶x2y-y2z+z2x
最后一道题应该是
x2y-y2z+z2x-x2z+y2x+z2y-2xyz

答案

6x²-5xy-6y²-2xz-23yz-20z² =6x^2-(5y+2z)x-6y^2-23yz-20z^2 =6[x^2-(5/6y+1/3z)x+(3/2y+2z)(-2/3y-5/3)z =6(x-3/2y+2z)(x+2/3y+5/3z) =(2x-3y+4z)(3x+2y+5z)x3+6x2+12x+9=X(X+3)2+3(X+3) =(x+3)(x2+...