Question

Me ajudem na equação do 2º grau. 3y(y+1)+(y-3)=y+9

Answer 1

3y(y+1)+(y-3)=y+9
4y+1+y-3=y+9
5y-2=y+9

Answer 2

$3y*(y+1)+y-3=y+9$

$3y*y+3y+y-3=y+9$

$3 y^{2} +3y+y-3=y+9$

$3 y^{2} +4y-3=y+9$

$3 y^{2} +4y-3-y=9$

$3 y^{2}+4y-3-y-9=0$

$3 y^{2} +4y-12-y=0$

$3 y^{2} +3y-12=0$    ⇒ DIVIDE-SE POR 3

$y^{2} +y-4=0$

Δ=$1^{2} -4(-4)$
Δ=$1^{2} +16$
Δ=$1+16$
Δ=$17$

$y_{1,2} = \frac{(-1)\± \sqrt{17} }{2}$

$y_{1,2} = \frac{(-1)\±4,123}{2}$

$y_{1} = \frac{(-1)+4,123}{2}$

$y_{1} = \frac{3,123}{2}$

$y_{1} = 1,562$

$y_{2} = \frac{-1-4,123}{2}$

$y_{2} = \frac{-5,123}{2}$

$y_{2} = -2,562$