Problem: When x is added to both the numerator and the denominator of the fraction ba​,aî€ =b,bî€ =0, the value of the fraction is changed to dc​. Then x equals:
Answer Choices:
A. c−d1​
B. c−dad−bc​
C. c+dad−bc​
D. c−dbc−ad​
E. c+dbc−ad​
Solution:
b+xa+x​=dc​∴ad+xd=bc+xc∴ad−bc=x(c−d)∴x=c−dad−bc​
Comment. If dc​=ab​,x=−(a+b).