[tex]15 x^{2} < \frac{1}{225} [/tex]  
 [tex]0.5 ^{8-x} =1[/tex]
[tex] \left \{ {{5x+2y=100} \atop {lgx-lgy=lg16-1}} \right. [/tex]
[tex] \sqrt{1-x}.\sqrt{x} =x[/tex]
[tex]( \sqrt{1,2} ) ^{4,2} ; ( \sqrt{1,2} ) ^{0,2} [/tex]