先把错误的结果分解因式,得到抄错的题目
6x" + 11x - 10
= 6x" + 15x - 4x - 10
= 3x( 2x + 5 ) - 2( 2x + 5 )
= ( 2x + 5 )( 3x - 2 )
-9x" - 9x + 10
= -9x" + 6x - 15x + 10
= -3x( 3x - 2 ) - 5( 3x - 2 )
= ( -3x - 5 )( 3x - 2 )
这样就看到,原先的 ( 2x + a )( 3x + b ),
应该 a = -5,b = -2,
正确的题目
( 2x - 5 )( 3x - 2 )
= 6x" - 4x - 15x + 10
= 6x" - 19x + 10
a= - 5 b= 2 6x^2-11x-10