lga+lgb=2lg(a-2b),求a/b的值Lg(ab)=Lg(a-2b)^2ab=(a-2b)^2ab=a^2-4ab+4b^25ab=a^2+4b^2,两边同除以b^2得5(a/b)=(a/b)^2+4(a/b)^2-5(a/b)+4=0[(a/b)-1][(a/b)-4]=0∴a/b=1或a/b=4