f(x)=(m-1)x^2+2mx+3m-3,
f(-x)=(m-1)(-x)^2=2mx+3m-3,
是偶函数
f(-x)=f(x)
(m-1)x^2+2mx+3m-3=(m-1)(-x)^2=2mx+3m-3,
4mx=0,
x=0,