What are the solutions of the equation x4 + 3x² + 2 = 0? Use u substitution to solve.
O x=+√√√2 and x = +1
Ox=ti√√2 and x = ti
Ox=± √√2 and x = ti
Ox=+√√2 and x = +1

Respuesta :

Answer:

[tex]\pm i\sqrt{2}\text{ and } \pm i[/tex]

Step-by-step explanation:

[tex]\text{let u = } x^2[/tex] so then [tex]u^2=x^4[/tex].

This gives you the equation: [tex]u^2+3u+2=0[/tex].

Now factor the equation by looking for factors of 2 that add up to 3, which is just 2 and 1. Use these to rewrite the equation: [tex](u+2)(u+1)[/tex]. So now just set each factor equal to 0:

[tex]u+2=0\\u=-2[/tex]

Now substitute x^2 back in as u

[tex]x^2=-2[/tex]

Take the square root of both sides

[tex]x=\pm \sqrt{-2}[/tex]

Separate the radical into sqrt(-1) * sqrt(2)

[tex]x=\pm \sqrt{-1}*\sqrt{2}[/tex]

Rewrite using i

[tex]x=\pm i\sqrt{2}[/tex]

Now set the other factor equal to 0

[tex]u+1=0\\u=-1[/tex]

substitute x^2 back in as u

[tex]x^2=-1[/tex]

Take the square root of both sides

[tex]x=\pm\sqrt{-1}[/tex]

rewrite using i

[tex]x=\pm i[/tex]