Răspuns:
7.
I : (x-4)(x-5)<0 =>x<{4,5}
II : (4-x)(-x-1)<0 =>x<{4} și x>{-1}
8.
rad[9-4rad5]=rad(9-80)=rad[(9+rad(81-80)/2] - rad[9-rad(81-80)/2]
=rad5 - 2
x(rad5 - 2)<_ 3rad5 - 6
x <_ (3rad5 - 6)/(rad5 - 2)
x <_ (3rad5 - 6)(rad5 + 2)/1
x <_ 15-12
x <_ 3 =>x € {1, 2, 3}
9.
x^2 + 2x + 1 - 3 <_ 0
x^2 + 2x - 2 <_ 0
delta=4-4•(-2)=4+8=12 =>rad.delta=2rad3
x1=(-2-2rad3)/2=(-1-rad3)
x2=(-2+2rad3)/2=rad3-1
