Question

（1）x³-x²y-xy²+y² （2）x²-8xy+15y²

Answer 1

1.似乎不可分解

2.=(x-3y)(x-5y)+2(x-3y)=(x-3y)(x-5y+2)

3.=(a-b)^2+4(a-b)+3=(a-b+1)(a-b+3)

4.1/2(2a^2+2b^2+2c^2-2ab-2bc-2ac)=1/2[(a-b)^2+(a-c)^2+(b-c)^2]=0

a-b=0

b-c=0

a-c=0

a=b=c