Question

Determine as raízes reais das equações incompletas:
a) x² - 5x = 0
b) -x² + 12x = 0
c) 5x² + x = 0
d) x² - 9x = 0

Answer 1

x² - 5x = 0
x(x - 5) = 0

x = 0

x - 5 = 0
x = 5


- x² + 12x = 0
x(- x + 12) = 0

x = 0

- x + 12 = 0
x = 12


5x² + x = 0
x(5x + 1) = 0

x = 0

5x + 1 = 0
5x = - 1
x = - 1/5


x² - 9x = 0
x(x - 9) = 0

x = 0

x - 9 = 0
x = 9

Answer 2

a) x² - 5x = 0

x • (x - 5)= 0

x= 0

x - 5= 0

x= 5

S= ( 0 , 5)

b) -x² + 12x = 0

x • ( - x + 12)= 0

x= 0

- x + 12= 0

- x= - 12(-1)

x= 12

S= ( 0 , 12)

c) 5x² + x = 0

x • (5x + 1)= 0

x= 0

5x + 1= 0

5x= - 1

x= - 1/5

S= ( 0 , - 1/5)

d) x² - 9x = 0

x • (x - 9)= 0

x= 0

x - 9= 0

x= 9

S= ( 0 , 9)