Question

 $x^{2} +3x=-9-3x$

Answer 1

$x^{2} +3x=-9-3x\\ \\ x^{2} +3x+9+3x=0\\ \\ x^{2} +6x+9\\ \\ \Delta=6^2-4.1.9=36-36=0\\ \\ \boxed{x=\frac{-6 \pm0}{2}=-3}$

Answer 2

 x² +3x= -9 -3x
x² + 3 x + 3 x + 9 =0
x² + 6 x +9 =0

Δ= b² - 4 . a . c
 
a=1,b= 6 e c=9

Δ= 6² -4 . 1 .9
Δ = 36 - 36
Δ=0, quando Δ=0,há duas raizes iguais
x=$\frac{-6+-0}{2} = \frac{-6}{2} = -3$

s (-3)