(9分)已知函數(shù)f ( x )=x
2+ax+b
(1)若f (x)為偶函數(shù),求實數(shù)a的值;
(2)若f (x)在
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內(nèi)遞增,求實數(shù)a的范圍.
(1)由f (x)="f" (-x),可得
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;
(2) ∵f (x)在
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內(nèi)遞增;∴

;
∴
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.
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