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3x^2+x-4=0; D=1^2-4*3*(-4)=1+48=49;  x1=(-1-7)/6, x2=(-1+7)/6. x1= -4/3, x2=1. 3x^2+x-4=3*(x+4/3)*(x-1)=(3x+4)*(x-1). получаем: (3x+4)*(x-1) / x*(x-1)=(3x+4) / x.