Question

Calcule as raízes da equação
a) 5x elevado a 2 - 20 = 0
b)7x elevado a 2 - 21 = 0
c)2x elevado a 2 + - 24 = 0

Answer 1

a) 5x^2 -20 =0
5x^2 = 20
(5x^2) ÷5 = 20 ÷5
x^2 = 4
x= raiz de 4

x=2

b) 7x^2 -21 =0
7x^2 = 21
x^2 = 3

x= raiz de 3

c) 2x^2 + (-24) =0
2x^2 -24 =0
2x^2 = 24
x^2 =12

x= raiz de 12

Answer 2

a)

5x² - 20 = 0
5x² = 20
x² = 20/5
x² = 4
x = √4
x = +/- 2
R.: x = 2 e x = - 2
¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨¨

b)
7x² - 21 = 0
7x² = 21
x² = 21/7
x² = 3
x = √3
R.: x = + √3 e x = - 3

***********************************
c)

2x² + x - 24 = 0
a = 2; b = 1; c = - 24

Δ = b² - 4ac
Δ = 1²  - 4.2.(-24)
Δ = 1 - 8.(-24)
Δ = 1 + 192
Δ = 193

x = - b +/- √Δ        - 1 +/- √193
      --------------  =  ----------------
            2a                  2.2

x' = - 1 + √193
     ----------------
              4

x" = - 1 - √193
      -------------
            4