Question

a(a+4)=5 cat face acest calcul?

Answer 1

a( a+4) = 5 <=> a² + 4a -5 =0

a=1

b=4

c= -5

Δ=b²-4ac

Δ=4²-4*1*(-5)

Δ= 16+20

Δ= 36 > 0

a₁,₂= -b ± √Δ /2 = -4+6/2

a₁ = -4+6/2 => a₁ = 2/2 = 1

a₂= -4-6/2 => x₂= -10/2 => a₂ = -5