Sa se rezolve ecuatia (x+1)(x+2)=56
Coeficientii sunt a=1, b=3, c=(-54)
Δ=b^2-4ac=3^2-4*1*(-54)=9-4*(-54)=9-[-(4*54)=9-(-216)=9+216=225>0,
iar √Δ=15.
Deci ecuatia are doua solutii reale, x1,2=[-(b)±√Δ]/(2a)=[(-3)±15]/(2*1)=[(-3)±15]/2.
x1=[(-3)-15]/2=[-(3+15)]/2=(-18)/2=[-(18/2)=(-9)
x2=[(-3)+15]/2=(15-3)/2=12/2=6
Multimea de solutii este S={(-9),6}.
Verificarea 1:
x=6
(6+1)(6+2)=56
7*8=56
56=56
Adevarat
Verificarea 2:
[(-9)+1][(-9)+2]=56
[-(9-1)[-(9-2)]=56
(-8)(-7)=56
8*7=56
56=56
Adevarat
