Помогите с алгеброй!

Решите задачу:

$1)\; (x^2-8)^2=x^2-8\\\\x^2-8=t, \; t^2=t\\\\t^2-t=0\\\\t(t-1)=0\\\\t_1=0,\; t_2=1\\\\a)\; x^2-8=0\\\\x^2=8\\\\x=\pm \sqrt8=\pm 2\sqrt2$

$b)\; x^2-8=1\\\\x^2=9\\\\x=\pm 3\\\\Otvet:\; -2\sqrt2,\; 2\sqrt2,\; -3,\; 3.$

$2)\; \left \{ {{\frac{y+1}{x-2}=0} \atop {x^2-y=5}} \right. \; \left \{ {{\frac{x^2-5+1}{x-2}=0} \atop {y=x^2-5}} \right. \\\\\frac{x^2-4}{x-2}=0\; \to \; \left \{ {{x^2-4=0} \atop {x-2\ne 0}} \right. \; \left \{ {{(x-2)(x+2)=0} \atop {x\ne 2}} \right. \; \left \{ {{x_1=-2,x_2=2} \atop {x\ne 2}} \right. \to \\\\x=-2,\; \; \to \; \; y=(-2)^2-5=-1\\\\Otvet:\; (-2,-1)$