Помогите решить логарифмические системы:
1) [tex] \left \{ {{ x^{2} + y^{2} =5} \atop { log_{2}x+ log_{2} y=1 }} \right. [/tex]
2) [tex] \left \{ {{ x^{2} - y^{2}=12 } \atop { log_{2}x- log_{2}y=1 }} \right. [/tex]
3) [tex] \left \{ {{ x^{2} + y^{2}=25 } \atop { lgx+lgy=lg12}} \right. [/tex]
4) [tex] \left \{ {{ log_{0,5} + log_{0,5}=-1 } \atop {x-2y=3}} \right. [/tex]