Resposta:
Y = x² - 4x + 3
x² - 4x + 3 = 0
∆ = b²-4ac
∆ = (-4)²-4.(1).(3)
∆ = 16-12
∆ = 4
x = -b±√∆/2a
x = -(-4)-2/2.1
x = 4-2/2
x = 2/2
x = 1
x = -(-4)+2/2.1
x = 4+2/2
x = 6/2
x = 3
S = {1, 3}
