x+1=t
x>1 t>2
则f(-t)=-f(t)
f(t)=2(t-1)^2-(t-1)+1=2t^2-5t+4
f(t)=2(t^2-5t/2+25/16-25/16)+4
f(t)=2(t-5/4)^2-7/8
f(-t)=2(t+5/4)^2-7/8(t>2)
t的减区间为[-5/4,+无穷)
所以x的减区间为[-5/4-1,+无穷)
[-9/4,+无穷)
x+1=t
x>1 t>2
则f(-t)=-f(t)
f(t)=2(t-1)^2-(t-1)+1=2t^2-5t+4
f(t)=2(t^2-5t/2+25/16-25/16)+4
f(t)=2(t-5/4)^2-7/8
f(-t)=2(t+5/4)^2-7/8(t>2)
t的减区间为[-5/4,+无穷)
所以x的减区间为[-5/4-1,+无穷)
[-9/4,+无穷)