Question

[TRẦN ĐÌNH BÌNH]

giúp em câu nay nưa nha :x^4-13x^2+36=0

Answer 1

[Đỗ Kim Lâm]

\(x^4-13x^2+36=0\)

\(\Leftrightarrow\)\(x^4-4x^2-9x^2+36=0\)

\(\Leftrightarrow\)\(x^2\left(x^2-4\right)-9\left(x^2-4\right)=0\)

\(\Leftrightarrow\)\(\left(x^2-9\right)\left(x^2-4\right)=0\)

\(\Leftrightarrow\)\(\left(x-3\right)\left(x+3\right)\left(x-2\right)\left(x+2\right)=0\)

\(\Leftrightarrow\) 1) x-3=0=>x=3

           2) x+3=0=>x=-3

           3) x-2=0=>x=2

           4) x+2=0=>x=-2

\(\Leftrightarrow S=\left\{-3;-2;2;3\right\}\)