( x + 1 )( x + 2 )( x + 3 )
这样的三个因式,一次项都是这一个 x,
分解因式就能用立方和、分组分解,
方式方法还不只一个。
= ( x + 1 )( x" + 5x + 6 )
= x"' + 5x" + 6x + x" + 5x + 6
= x"' + 6x" + 11x + 6
得到题目,分解因式,做给你看吧
= x"' + 1 + 6x" + 11x + 5
= x"' + 1"' + 6x" + 6x + 5x + 5
= ( x + 1 )( x" - x + 1 ) + 6x( x + 1 ) + 5( x + 1 )
= ( x + 1 )( x" - x + 6x + 5 + 1 )
= ( x + 1 )( x" + 5x + 6 )
= ( x + 1 )( x + 2 )( x + 3 )
或者
= x"' + 8 + 6x" + 11x - 2
= x"' + 2"' + 6x" + 12x - x - 2
= ( x + 2 )( x" - 2x + 4 ) + 6x( x + 2 ) - ( x + 2 )
= ( x + 2 )( x" - 2x + 6x - 1 + 4 )
= ( x + 2 )( x" + 4x + 3 )
= ( x + 2 )( x + 3 )( x + 1 )
还有
= x"' + 27 + 6x" + 11x - 21
= x"' + 3"' + 6x" + 18x - 7x - 21
= ( x + 3 )( x" - 3x + 9 ) + 6x( x + 3 ) - 7( x + 3 )
= ( x + 3 )( x" - 3x + 6x - 7 + 9 )
= ( x + 3 )( x" + 3x + 2 )
= ( x + 3 )( x + 2 )( x + 1 )