Question

Решите уравнение
4^x +2^x-20=0

Answer 1

$4^{x}+2^{x}-20=0$

Сделаем замену :

$2^{x}=m,m>0 \\\\m^{2}+m-20=0\\\\D=1^{2}-4*(-20)=1+80=81=9^{2}\\\\m_{1}=\frac{-1+9}{2}=4\\\\m_{2}=\frac{-1-9}{2}=-5<0\\\\2^{x}=4\\\\2^{x}=2^{2}\\\\x=2$

Ответ : 2

Answer 2

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