(1+√5)/2= calculator=1,618...≈1,6
b) fie ecuatia
x²-x-1=0
a=1
b=-1
c=-1
rezolvand cu Δ, obtinem x1,2=(1+-√5)/2
dacesti a 7-a si nu ai invatat ec de grad 2, calcul direct
[(1+√5)/2]²-(1+√5)/2=1
(1+5+2√5)/4-1/2-√5/2=1
6/4+√5/2-1/2-√5/2=1
3/2-1/2=1
2/2=1
1=1
adevarat
