Question

Achar as raízes das equações 

a) x²- x-20 = 0
b)x² - 3x-4=0
c)x² - 8x + 7 =0  

Answer 1

a)x²-x-20=0
$x= \frac{-(-1)+/- \sqrt{-1^2-4.1.(-20)} }{2.1}$
$x= \frac{1+/- \sqrt{81} }{2}$
$x= \frac{1+/-9}{2}$
$x^1= \frac{10}{2} =5$
$x^2= \frac{8}{2} =4$
Guenta ae que eu vo botando aos poucos, demora pra fazer esses calculos.
B)x^2-3x-4=0
$x= \frac{-(-3)+/- \sqrt{(-3)^2-4.1.(-4)} }{2.1}$
$x= \frac{3+/- \sqrt{5} }{2}$
$x^1= \frac{8}{2} = 4$
$x^2= \frac{-2}{2} =-1$

C)x^2-8x+7=0
$x= \frac{-(-8)+/- \sqrt{(-8)^2-4.1.7} }{2.1}$
$x= \frac{8+/- \sqrt{36} }{2}$
$x= \frac{8+/-6}{2}$
$x^1= \frac{14}{2} =7$
$x^2= \frac{2}{2} =1$

Answer 2

a) x²- x-20 = 0

a= 1     b= -1     c= -20
▲= b² -4.a.c= (-1)² -4.(1).(-20)= 1 + 80= 81

x= (-b ± √▲)/2.a
x= [-(-1) ± √81]/2.1
x= [+1 ± 9]/2
x'=[1+9]/2 = 10/2= 5
x"=[1-9]/2 = -8/2 = -4

S{5 e -4}

b)x² - 3x-4=0

a= 1     b= -3      c= -4
▲= b² -4.a.c = (-3)² -4.(1).(-4)= 9 +16= 25

x= (-b ± √▲)/2.a
x=[-(-3) ± √25]/2.1
x'=[+3 ± 5]/2 = 8/2= 4
x"=[3-5]/2= -2/2= -1

S{4 e -1}


c)x² - 8x + 7 =0

a= 1      b= -8       c= +7
▲= b² -4.a.c = (-8)² -4.(1).(+7)= 64 - 28= 36

x= (-b ± √▲)/2.a
x=[-(-8) ± √36]/2.1
x=[+8 ± 6]/2
x'=[8+6]/2= 14/2=7
x"=[8-6]/2= 2/2= 1

S{ 7 e 1 }