If the question is |x||x|>=≥ 0 you have that xx <=≤ 0 or 0<=≤xx. But every number verifies that. In fact if xx is a negative number x<0x<0 and if it's positive x>0x>0, finally if it's 00 then x=0x=0. Then x x must be in (-oo,oo)(−∞,∞) which is x in RR