Question

calcule (5+3i).(2-4i)

Answer 1

Δ10-9i+6i-12i²

-12i²-3i+10
a = -12, b = -3, c = 10

Δ = b²-4ac
Δ = -3²-4*(-12)*10
Δ = 9+480
Δ = 489

x = (-b+-√Δ)/2a
x = (-(-3)+-√489)/2*(-12)
x = (3+-√489)/-24