X-y=6 y=x-6 xy=4x+y x(x-6)=4x+x-6 x²-6x=4x+x-6 x²-11x+6=0 D=121-24=97 √D=√97 x1=1/2[11-√97] x2=1/2[11+√97] y1=1/2[11-√97]-6 y2=1/2[11+√97]-6