(1) x^2-3xy-10y^2+x+9y-2= (x-5y+2)(x+2y-1)
(2) x^2-y^2+5x+3y+4= (x+y+1)(x-y+4)
(3) xy+y^2+x-y-2= (y+1)(x+y-2)
(4) 6x^2-7xy-3y^2-xz+7yz-2z^2= (2x-3y+z)(3x+y-2z)
(5)x^2+5xy+6y^2+8x+18y+12=（x+2y+2)(x+3y+6)
(6)a^2 (b-c)+b^2 (c-a)+c^2 (a-b)
= a^2(b-c)+b^2c-ab^2+ac^2-bc^2
= a^2(b-c)-a(b^2-c^2)+(b^2c-bc^2)
= (b-c) [a^2 -a(b+c)+bc]
= (b-c)(a-b)(a-c) （选定a为主元,将其按次数从高到低排列,后采用适当方法进行分解.）