[tex] x^{2} +2x+x+2=56[/tex]
[tex] x^{2} +3x+2-56=0[/tex]
[tex] x^{2} +3x-54=0[/tex]
[tex]delta=b^2-4ac [/tex]
[tex]delta=3^2-4*1*(-54)=9+216=225 <=> \sqrt{225}=15[/tex]
[tex] x_{1} =(-b+15)/2a=-3+15/2=12/2=6[/tex]]
[tex] x_{2} =(-b-15)/2a=-3-15/2=-18/2=-9[/tex]
x∈{6,-9}
