a)
2 x - 10 = 0
2 x = 10
x = 10 : 2
x = 5
____________________
b)
x² - 5 x + 6 = 0
Δ = 25 - 24 = 1
x = ( 5 + 1 ) / 2 = 6 / 2 = 3
x = ( 5 - 1 ) / 2 = 4 / 2 = 2
3 x + 8 = x + 16
3 x - x = 16 - 8
2 x = 8
x = 8 : 2
x = 4
______________________
c)
x² - 5 x + 6 = 0
Δ = 25 - 24 = 1
x₁ = ( 5 + 1 ) / 2 = 6 / 2 = 3
x₂ = ( 5 - 1 ) / 2 = 4 / 2 = 2