Question

206x(в 4-ой степени)-205x(во второй степени )-1=0

Answer 1

$206x^{4} - 205 x^{2} -1=0$
[tex] x^{2}=t, x^{4} = t^{2} \ 206 t^{2} -205t-1=0 \ D = 205 ^{2} +4*206=42849 \
 t _{1} = frac{ 205+sqrt{42849} }{2*206} = frac{412}{412}=1 \ t_{2} =frac{ 205-sqrt{42849} }{2*206}= frac{-1}{206} \ x^{2} =t; x^{2} =1 и \ x_{1/2} =1