Question

x(x+5)-2x=28
resolva a equação segundo grau​

Answer 1

X(x+5)-2x=28
x^2 + 5x - 2x = 28
x^2 + 3x - 28 = 0
a = 1; b = 3; c = - 28
/\= b^2 - 4ac
/\= 3^2 - 4.1.(-28)
/\= 9 + 112
/\= 121

X = (-b +/- \/ /\)/2a
X = (-3 +/- \/121)/2.1
x = (-3 +/- 11)/2

x ' = (-3-11)/2= - 14/2= - 7
x " = (-3+11)/2= 8/2= 4

Answer 2

$\sf x(x+5)-2x=28$

$\sf x^2+5x-2x=28$

$\sf x^2+3x-28=0$

$\begin{cases}\sf a=1\\\sf b=3\\\sf c=-28\end{cases}$

$\sf\Delta=b^2-4\cdot a\cdot c$

$\sf\Delta=3^2\cdot1\cdot(-28)$

$\sf\Delta=9+112$

$\sf \Delta=121$

$\sf x=\dfrac{-b\pm\sqrt{\Delta}}{2\cdot a}$

$\sf x=\dfrac{-3\pm\sqrt{121}}{2\cdot1}$

$\sf x=\dfrac{-3\pm11}{2}\begin{cases}\sf x_1=\dfrac{-3+11}{2}=\dfrac{8}{2}=4\\\\\sf x_2=\dfrac{-3-11}{2}=\dfrac{-14}{2}=-7\end{cases}$

$\boxed{\boxed{\sf S=\big\{-7;4\big\}}}$