Question

Achar as raízes das equações:
a) x*-x-20=0
b) x*-3x-4=0
c) x*-8x+7=0

Answer 1

a)a=1  b=-1   c=-20
Δ=b²-4ac
Δ=(-1)²-4.1.(-20)  x1=1+9/2=10/2=5   x2=1-9/2=-8/2=-4,As raizes são -4 e 5
Δ=1+80
Δ=81
b)a=1 b=-3  c=-4 x1'=3+5/2=8/2=4  x2=3-5/2=-2/2=-1,As raizes são-1,4
Δ=(-3)²-4.1.(-4)
Δ=9+16
Δ=25
c)a=1   b=-8   c=7
Δ=(-8)²-4.1.7    x1=8+6/2=14/2=7 x2=8-6/2=2/2=1,As raizes são 1,7
Δ=64-28
Δ=36

Answer 2

Olá!!!

x² - x - 20 <== a)

a = 1
b = - 1
c = - 20

▲ = b² - 4ac
▲ = ( - 1 )² - 4 • ( - 1 ) • ( - 20 )
▲ = 1 + 80
▲ = 81

x = - b ± √▲ / 2a
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 , - 4 } => ( Raízes)

x² - 3x - 4 = 0 <== b)

a = 1
b = - 3
c = - 4

▲ = b² - 4ac
▲ = ( - 3 )² - 4 •1 • ( - 4 )
▲ = 9 + 16
▲ = 25

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

S = { 4 , - 1 } => ( Raízes)

x² - 8x + 7 = 0 <== c)

a = 1
b = - 8
c = 7

▲ = b² - 4ac
▲ = ( - 8 )² - 4 • 1 • 7
▲ = 64 - 28
▲ = 36

x = - b ± √▲ / 2a
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 , 1 } => ( Raízes )

Espero ter ajudado... uffa!! rsrs...