1/2log(10)(x+6)加log(10)(根号2x+5)=log(10）(6根号2);lg[根号(x+6)]+lg[根号(2x+5)]=lg根号72;lg[根号(x+6)]*[根号(2x+5)]=lg根号72;[根号(x+6)]*[根号(2x+5)]=根号72;(x+6)*(2x+5)=72;2x^2+17x-42=0;;x=2;x=-21/2...