Răspuns :

(x-3)(x+4)=0
x²+4x-3x-12=0
x²+x-12=0
Δ=b²-4ac
Δ=1+48⇒Δ=49; √Δ=7
x1=(-1+7)÷2; x1=3
x2=(-1-7)÷2; x2=-4
a) x1=3; x2=-4