Question

若f(x)=(k-2)X^2+(k-1)X+3是偶函数,则f(x)的递增区间是什么?

Answer 1

f(x)=(k-2)X^2+(k-1)X+3是偶函数==>f(-x)=f(x)==>(k-2)(-x)^2+(1-k)x+3=(k-2)X^2+(k-1)X+3==>k=1==>f(x)=-X^2+3

之后就简单啦,负无穷到0么,