Question

Решите системы логарифмических уравнений: 1) 2) 3) 4)

Answer 1

$1) \left \{ {{lgx-lgy=-lg2} \atop {y=1.5x+1}} \right. \left \{ {{lg\frac{x}{y}=lg2^{-1}} \atop {y=1.5x+1}} \right. \left \{ {{\frac{x}{y}=0.5} \atop {y=1.5x+1}} \right. \left \{ {{x=0.5y} \atop {y=0.75y+1}} \right. \left \{ {{y=4} \atop {x=2}} \right. \\ 2) \left \{ {{log_2(x+y)+log_2(x^2-xy+y^2)=log_22} \atop {x=y}} \right. \left \{ {{x^3+y^3=2} \atop {x=y}} \right. \left \{ {{y=1} \atop {x=1}} \right. \\ 3) \left \{ {{2x-y=2} \atop {lg(x+2)=lg16}} \right. \left \{ {{y=2x-2} \atop {x=14}} \right. \left \{ {{y=26} \atop {x=14}} \right. \\$
$4)\left \{ {{7.5(y-x)=xy} \atop {log_3xy=log_315}} \right. \left \{ {{7.5(y-x)=xy} \atop {7.5(y-x)=15}} \right. \left \{ {{y-x=2} \atop {15=xy}} \right. \left \{ {{y=x+2} \atop {x^2+2x-15=0}} \right. \left \{ {{x=3, x=-5} \atop {y=5, y=-3}} \right.$, но y и x должны быть больше 0, поэтому пара (-5;-3) не подходит