Question

Por favor alguém me ajuda!

Answer 1

Olá Edesson

x² - x - 20 = 0 

delta
d² = 1 + 80 = 81
d = 9

x1 = (1 + 9)/2 = 10/2 = 5
x2 = (1 - 9)/2 = -8/2 = -4

x² - 3x - 4 = 0

delta
d² = 9 + 16 = 25
d = 5

x1 = (3 + 5)/2 = 8/2 = 4
x2 = (3 - 5)/2 = -2/2 = -1 

Answer 2

a)
achar o delta
∆=b²-4ac
∆=-1²-4.1.(-20)
∆=1+80
∆=81

aplicando baskara

x'=-b+√∆ x"=-b-√∆
2a 2a
x'=-(-1)+√81 x"=-(-1)-√81
2.1 2.1
x'=1+9 x"=1-9
2 2
x'=10/2 x"=-8/2
x'=5 x"=-4
S={5,-4}

b)∆=(-3)²-4.1(.-4)
∆=9+16
∆=25

x'=-(-3)+√25/2.1
x'=3+5/2
x'=8/2
x'=4

x"=-(-3)-√25/2.1
x"=3-5/2
x"=-2/2
x"=-1
S={4,-1}