Question

Quero a conta.
-x^2 -x +20 =0
Resposta correta→ v={-5,4}
Me ajudem por favor!!

Answer 1

-x² - x + 20 = 0

x² + x - 20 = 0

∆ = 1² - 4.1.(-20)

∆ = 1 + 80

∆ = 81

$x = \frac{ - 1 + - \sqrt{81} }{2 \times 1}$

$x = \frac{ - 1 + - 9}{2}$

$x1 = \frac{ - 1 + 9}{2} \\ x2 = \frac{ - 1 - 9}{2}$

$x1 = 4 \\ x2 = - 5$

Answer 2

Resposta:

-x²-x+20=0

Multiplicando tudo por (-1)

x²+x-20=0

$Aplicando~a~f\'{o}rmula~de~Bhaskara~para~x^{2}+x-20=0~~\\e~comparando~com~(a)x^{2}+(b)x+(c)=0,~temos~a=1{;}~b=1~e~c=-20\\\\\Delta=(b)^{2}-4(a)(c)=(1)^{2}-4(1)(-20)=1-(-80)=81\\\\x^{'}=\frac{-(b)-\sqrt{\Delta}}{2(a)}=\frac{-(1)-\sqrt{81}}{2(1)}=\frac{-1-9}{2}=\frac{-10}{2}=-5\\\\x^{''}=\frac{-(b)+\sqrt{\Delta}}{2(a)}=\frac{-(1)+\sqrt{81}}{2(1)}=\frac{-1+9}{2}=\frac{8}{2}=4\\\\S=\{-5,~4\}$