下列各式因式分解题目及答案:
(1) X3+7X2+X+7 (2) X3+3X2-5X-15
详解:
(1) X3+7X3+X+7
= (X3+7X2)+(X+7) (分组)
= X2(X+7)+(X+7) (在X3+7X2中提出X2)
= (X2+1)(X+7) (提出X+7)
(2) X3+3X2-5X-15
= X3+3X2-(5X+15) (分组)
= X2(X+3)-5(X+3) (在X3+3X2中提出X2,5X+15中提出 5)
= (X2-5)(X+3) (提出X+3)
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