Question

Alguem me ajuda nesse negocio aqui? PFVR

$x^{4} - 4 = 3x^{2}$
$x^{4} - 16 x^{2} = 0$

Answer 1

$a) x^{4}-4=3 x^{2} \\ x^{4}-3 x^{2} -4=0 \\ x^{2} =y \\ y^{2} -3y-4=0 \\ deltay=9-4.1.(-4)=9+16=25 \\ y_{1} = \frac{3+5}{2}=4 \\ y_{2}= \frac{3-5}{2}=-1 \\ x= \sqrt{4}= +/-2 \\ para,y=-1,x,nao,existe \\ b) x^{4}-16 x^{2}=0 \\ x^{2} =y \\ y^{2}-16y=0 \\ y(y-16)=0 \\ logo \\ y=0 \\ ou \\ y=16 \\ entao \\ x=0 \\ ou \\ x= \sqrt{16} \\ x=+/-4$