9 2x^2-7x+6=(x-2)(2x-3) y^4-10y^2+9=(y^2-1)(y^2-9)=(y-1)(y+1)(y+3)(y-3)
10 前面一个你写得是对的 (1-m)(m^2+m+1)=m^3-1
11(a-1/a)^2=2 a^2+1/a^2-2=2 a^2+1/a^2=2+2=4 2x=0 x=0
12(±6) x^2+4x+y^2-2y+5=0 (x^2+4x+4)+(y^2-2y+1)=0 (x+2)^2+(y-1)^2=0 x+2=0 x=-2 y-1=0 y=1 xy=-2
下面的都没图呀