Question

Resolva as seguintes equações do 2º grau,sendo U=R.

a)x² - 9 = 0

b) 4² - 25 = 0

c) 9x² = 49

d) x² - 2 = 0

e) 8x² - 320 = 0

f) -x² + 2x = 0

g) x² - 15x = 0

h) 5x² + x = 0

i) 4x² - 36x = 0

Answer 1

a)x² - 9 = 0

x²= 9

x= ± √9

x= ± 3

S= ( 3 , - 3)

b) 4x² - 25 = 0

4x²= 25

x²= 25/4

x= ± √25/4

x= ± 5/2

S= ( 5/2 , - 5/2)

c) 9x² = 49

x²= 49/9

x= ± √49/9

x= ± 7/3

S= ( 7/3 , - 7/3)

d) x² - 2 = 0

x²= 2

x= ± √2

S= ( √2 , - √2)

e) 8x² - 320 = 0

8x²= 320

x²= 320/8

x²= 40

x= ± √40

S= ( √40 , - √40)

f) -x² + 2x = 0

x • ( - x + 2)= 0

x= 0

- x + 2= 0

- x= - 2(-1)

x= 2

S= ( 0 , 2)

g) x² - 15x = 0

x • (x - 15)= 0

x= 0

x - 15= 0

x= 15

S= ( 0 , 15)

h) 5x² + x = 0

x • (5x + 1)= 0

x= 0

5x + 1= 0

5x= - 1

x= - 1/5

S= ( 0 , - 1/5)

i) 4x² - 36x = 0

x • (4x - 36)= 0

x= 0

4x - 36= 0

4x= 36

x= 36/4

x= 9

S= ( 0 , 9)