Question

determine as raízes da questão..
x² = 81
x² = 100
(x-7)² = 0
(x + 5)² = 0

Answer 1

x² = 81
x = +- √ 81
x = +- 9

S = { 9 ; - 9 }

x² = 100
x = +- √ 100
x = +- 10

S = { 10 ; - 10}

(x-7)² = 0
(x - 7) . ( x - 7) = 0
x^2 - 7x - 7x + 49 = 0
x^2 - 14x + 49 = 0
x = 14 +- 0/2
x' e x" = 7

(x + 5)² = 0
(x + 5) . (x + 5) = 0
x^2 + 5x + 5x + 25 = 0
x^2 + 10x + 25 = 0
x = - 10 +- 0/2
x' e x" = - 5

Espero ter ajudado.

Answer 2

a)
x² = 81
x = √81
x = + 9 e x = - 9
========================
b)
x² = 100
x = √100
x = + 10 e x = - 10
==========================
c)
(x - 7)² = 0

(x - 7).(x - 7) = 0

x - 7 = 0
x = 7

ou:

x² - 2.7x + 49 = 0
x² - 14x + 49 = 0
a = 1; b = - 14; c = 49

Δ = b² - 4ac
Δ = (-14)² - 4.1.49
Δ = 196 - 196
Δ = 0

x = - b +/- √Δ  = - ( - 14) +/- 0
          2a                   2.1

x = 14 =  7 
       2 

R.: x = 7
===========================
d)
(x + 5)² = 0

(x + 5).(x + 5) = 0
x + 5 = 0
x = - 5

ou:

x² + 2.5x + 25 = 0
x² + 10x + 25 = 0
a = 1; b = 10; c = 25

Δ = b² - 4ac
Δ = 10² - 4.1.25
Δ = 100 - 100
Δ = 0

x = - b +/- √Δ = - 10 +/- 0
            2a              2.1

x = - 10 = - 5
         2

R.: x = - 5