6-x=10 => -x=4 => x=-4
72:x=-9 => x=-8
5-x=10-x => x-x=10-5 => 0=5 => imposibil
3x+10+x=2+4x+8 => 4x-4x=10-10 => 0=0 => x=0
6-3(x+1)=7x-7 => 6-3x-3=7x-7 => -10x=-10 => x=1
12-3x[2-2(2-x)]:2=36 => 12-3x[2-4+2x]=72 => 12-6x+12x-6x^2=72 =>
=> -6x^2+6x-60=0 => x^2+x-10=0 iar cum delta e negativ => imposibil (suntem in multimea Z)
x^2-x=6 => x^2-x-6=0
delta = (-1)^2 -4*-6 = 25 => x1 = -2, x2 = 3 deci x poate fi -2 sau 3
