2.
Numitor comun 6
2(x-3)^2 - 3(1-x^2) = 5x^2 + 9x - 2 - 18
2(x^2 - 6x + 9) - 3 + 3x^2 = 5x^2 + 9x - 20
5x^2 - 12x + 15 = 5x^2 + 9x - 20
-12x - 9x = -20 - 15
-21x = -35
x = 35/21 = 5/3
3.
rad(7-rad48) = rad{[7+rad(49-48)]/2} - {[7-rad(49-48)]/2 = 2 - rad3
2rad3 - x•(2 - rad3) = 3
-x(2-rad3)=3-2rad3
x=(2rad3-3)/(2-rad3)
x=(2rad3-3)(2+rad3)/1
x=4rad3+6-6-3rad3
x=rad3
