Ответы и объяснения

2013-04-23T19:04:30+04:00

0.3х(х+13)-2х(0.9-0.2х)=0

0.3x^2+3.9x-1.8x+0.4x^2=0

0.7x^2+2.1x=0

x(0.7x+2.1)=0

x=0        0.7x+2.1=0

              0.7x=-2.1

              x=-3