(3x+V2)(3-xV2)=7 =>
9x+3V2-3x²V2-2x=7 =>
7x+3V2(1-x²)-7=0 =>
7(x-1)-3V2(x²-1)=0 =>
7(x-1)-3V2(x+1)(x-1)=0=>
(x-1)(7-3V2x-3V2)=0 => x-1=0=>x=1
sau 7-3V2x-3V2=0 => 7=3V2x+3V2 => 7=3V2(x+1)=>
x+1=7/3V2 => x+1=7V2/6=>x=(7V2-6)/6
x€Z => x=1 solutie => B={1}