f(x)=2x-x^2 (x>=0)
设x<=0
-x>=0
f(x)=f(-x)
=2(-x)-(-x)^2
=-2x-x^2 (x<=0)
f(x)ç解æå¼ï¼
f(x)=2x-x^2 (x>=0)
f(x)=-2x-x^2 (x<=0)
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(1)x>=0æ¶
f(x)=2x-x^2
=-(x-1)^2+1
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(2)x<=0æ¶
f(x)=-2x-x^2
=-(x+1)^2+1
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