实数a

问题描述:

实数a

( a" + b" ) / ( a + b )= ( a" + 2ab + b" - 2ab ) / ( a + b )= [ ( a + b )" - 2 ] / ( a + b )= ( a + b )" / ( a + b ) - 2 / ( a + b )= - ( a + b ) - 2/(a + b)