Question

Resolva as equações.

a)
${x }^{2} - 90 = 31$

b)
$5 {x}^{2} + 4 = 49$

c)
$4 {x}^{2} - 27 = {x}^{2}$

d)
$2 {x}^{2} + 11 = {x}^{2} + 12$

e)
$5 {(x}^{2} - 1) = 4( {x}^{2} + 1)$

f)
$x(x + 2) = 2x + 25$
​

Answer 1

a) x² - 90 = 31

x² = 31 + 90

x² = 121

x = ± √121

x = ± 11

b) 5x² + 4 = 49

5x² = 49 - 4

5x² = 45

x² = 45/5

x² = 9

x = ± √9

x = ± 3

c) 4x² - 27 = x²

4x² - x² = 27

3x² = 27

x² = 27/3

x² = 9

x = ±√9

x = ± 3

d) 2x² + 11 = x² + 12

2x² - x² = 12 - 11

x² = 1

x = ± √1

x = ± 1

e) 5(x² - 1) = 4(x² + 1)

5x² - 5 = 4x² + 4

5x² - 4x² = 4 + 5

x² = 9

x = ±√9

x = ± 3

f) x(x + 2) = 2x + 25

x² + 2x = 2x + 25

x² + 2x - 2x = 25

x² = 25

x = ±√25

x = ± 5