Question

2lgx-lg 4=-lg(5-x^2) логарифмическое уравнение 

Answer 1

$2lg x-lg 4=-lg(5-x^2)\2lg x=lg4-lg(5-x^2)\ leftlbracebegin{array}{l} x>0\x^2=frac{4}{5-x^2}end{array}right.\leftlbracebegin{array}{l} x>0\x^2(5-x^2)=4end{array}right.\leftlbracebegin{array}{l} x>0\x^4-5x^2+4=0end{array}right.\leftlbracebegin{array}{l} x>0\(x^2-1)(x^2-4)=0end{array}right.\ left[begin{array}{l}x=1\x=2 end{array}right.$