Question

设三个正数a,b,c为等差数列,x为a与b的等比中项,y为b与c的等比中项；求证：x平方b平方y平方成等差数列

Answer 1

2b=a+c,x^2=ab,y^2=bc,2b^2=2b*b=(a+c)*b=ab+ac=x^2+y^2