Question

15 x ao quadrado menos 5x igual a zero

Answer 1

15x² - 5x = 0 :(5)
3x² - x = 0
x.(3x - 1) = 0
x' = 0
3x-1 = 0
3x = 1
x" = 1/3

Answer 2

15 x²  -  5 x = 0
5 x(3 x - 1) = 0
5 x = 0 
x = 0/5 
x´ = 0
3 x - 1 =0
3 x = 1
x" = 1/3
S={0,1/3}