2(x-3)(3+2x)<=x <=> 2(2x^2-3x-9)<=x <=> 4x^2-6x-18<=x <=> 4x^2-7x-18<=0 <=> (2x-7/4)^2-49/16-18<=0 <=> (2x-7/4)^2<=337/16 <=> |2x-7/4|<=rad(337)/4 <=> -rad(337)/4<=2x-7/4<=rad(337)/4 <=> (7-rad(337))/4<=2x<=(7+rad(337))/4 <=> (7-rad(337))/8<=x<=(7+rad(337))/8 <=> x apartine [(7-rad(337))/8,(7+rad(337))/8].
