Question

已知a+b+c=0,a+2b+3c=0,且abc ≠0,求(ab+bc+ac)/b的值?

Answer 1

A,B,C都不等于0 a+b+c=0,(1) a+2b+3c=0 (2) (2)-(1):B+2C=0 ==>B=-2C ,A=C 所以(ab+bc+ca)/b^2=(C*(-2C)+(-2C)*C+C*C)/(-2C)^2=-3C^2/(4C^2)=-3/4