1/3(a+2b)+1/4(3a-2b)-1/2(a-b)
=1/3a＋3/4a-1/2a＋2/3b-1/2b＋1/2b
=7/12a＋2/3b若2/3(4a-3x)+3(5x-4b)=0,其中ab为向量,求向量x2/3(4a-3x)+3(5x-4b)=08/3a-2x＋15x-12b=013x=-8/3a＋12bx=-8/39a＋12/13b