Question

x^3-8x-9=0. Aflati x

Answer 1

$x^{3}+8x-9=0 \\ (x^3-1)+(8x-8)=0 \\ (x-1)(x^2+x+1)+8(x-1)=0 \\ (x-1)[ x^{2} +9x-7]=0 \\ x=1;sau: x^{2} +9x-7=0$
Δ=81+49=130
$x_{1}= \frac{-9+ \sqrt{130} }{2} \\ x_{2}= \frac{-9- \sqrt{130} }{2}$