Explicație pas cu pas:
a) 1O2=2(1+2-1)-1*2=2*2-2=2 (adevarat)
b)xO2=2(x+2-1)-2x =2(x+1)-2x=2x+2-2x=2
c) xOx=x => 2(x+x-1)-x²=x => 2(2x-1)-x²=x=>4x-2-x²=x
=>3x-2-x²=0
=>x²-3x+2=0
=>x²-x-2x+2=0
=>x(x-1)-2(x-2)=0
=>(x-1)(x-2)=0=>x1=1 sau x2=2
S€{1,2}