a比b=c比d=7比5 求2b-3d分之2a-3c

问题描述:

a比b=c比d=7比5 求2b-3d分之2a-3c

a比b=c比d=7比5
a=7b/5
c=7d/5
2b-3d分之2a-3c
=(2*7b/5-3*7d/5)/(2b-3d)
=7/5(2b-3d)/(2b-3d)
=7/5