x^2+2(a-4)x-3a+2=0
x^2+2(a-4)x=3a-2
x^2+2(a-4)x+(a-4)^2=3a-2+a^2-8a+16
(x+a-4)^2=a^2-5a+14
x+a-4=±√(a^2-5a+14)
x=±√(a^2-5a+14)-a+4
x1=√(a^2-5a+14)-a+4>2
√(a^2-5a+14)>a-2
a^2-5a+14)>a^2-4a+4
a^2-a^2-5a+4a+14-4)>0
-a+10>0
a4-a
a^2-5a+14>a^2-8a+16
a^2-a^2-5a+8a+14-16>0
3a>2
a>2/3
所以2/3