a的相反数是一又三分之二, 则a=-5/3
b的相反数是负二又二分之一, 则b=5/2
所以(a-2b)/(a+3b)=(-5/3-5)/(-5/3+15/2)
=(-10-30)/(-10+45)
=-40/35
=-8/7
a=-5/3,b=5/2, (a-2b)/(a+3b)=(-5/3-5)/(-5/3+15/2)=-40/35=-8/7
结果为:负的7分之37
-a=1又2/3,则a=-1又2/3;
-b=-2又1/2,则b=2又1/2.
(a-2b)/(a+3b)
=(-1又2/3-2*2又1/2)/(-1又2/3+3*2又1/2)
= -8/7 (负七分之八)