【正文】
得 ( x + 5 )( x + n ) ,則 m = __ , n = __ . 【解析】 ( x + 5)( x + n ) = x 2 + (5 + n ) x + 5 n = x 2 + mx+ 5 ,則??? 5 + n = m ,5 n = 5 ,解得??? m = 6 ,n = 1. (x- 2) (x- 1) 6 1 7. 把多項(xiàng)式 a2- 4 a 分解因式,結(jié)果正確的是 ( ) A . a ( a - 4 ) B . ( a + 2 )( a - 2 ) C . a ( a + 2 )( a - 2 ) D . ( a - 2 )2- 4 8. 下列因式分解正確的是 ( ) A . 2 x2- 2 = 2 ( x + 1 )( x - 1 ) B . x2+ 2 x - 1 = ( x - 1 )2 C . x2+ 1 = ( x + 1 )2 D . x2- x + 2 = x ( x - 1 ) + 2 A A 9. 下列各式從左邊到右邊的變形: ① 15 x2y = 3 x 5 xy ;② ( x + y )( x - y ) = x2- y2; ③ x2- 2 x + 1 = ( x - 1 )2; ④ x2-3 x + 1 = x????????x - 3 +1x,其中是因式分解的有 ( ) A . 0 個(gè) B . 1 個(gè) C . 2 個(gè) D . 3 個(gè) 10. 已知多項(xiàng)式 2 x2+ bx + c 因式分解為 2 ( x - 3 )( x +1 ) ,則 b , c 的值為 ( ) A . b = 3 , c =- 1 B . b =- 6 , c = 2 C . b =- 6 , c =- 4 D . b =- 4 , c =- 6 B D 1 1. 因