(1)通過原點表示x=0,將x代入f(x)即f(0) = (a+2)*0 + b = 0 => b = 0 (2)若f(x)為常數函數,即其非常數項的係數皆為零,在本例中就是x的係數(a+2)為零,也就是(a+2) = 0,得出的解即a = -2 (3)f(x)為一次函數,即其一次項的係數不為零,常數項任意,在本例中就是x的係數(a+2)不為零,而不為零的條件,就是為零的條件以外的所有條件,在本例中就是a勿能等於-2
以上是我個人見解
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