x^3=-8i

Lösung

x^{3} = - 8 i

x = 3 - i, x = 2 i, x = - 3 - i

Schritte zur Lösung

x^{3} = - 8 i

Für

z^{n} = a

sind die Lösungen

z_{k} = n ∣ a ∣ (cos (\frac{ar g ( a ) + 2 kπ}{n}) + i sin (\frac{ar g ( a ) + 2 kπ}{n})),

k = 0, 1, \dots, n - 1

Für

n = 3, a = - 8 i

∣ a ∣ = 8

ar g (a) = - \frac{π}{2}

x = 38 (cos (\frac{- \frac{π}{2} + 2 \cdot 0 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 0 π}{3})), x = 38 (cos (\frac{- \frac{π}{2} + 2 \cdot 1 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 1 π}{3})), x = 38 (cos (\frac{- \frac{π}{2} + 2 \cdot 2 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 2 π}{3}))

Vereinfache

38 (cos (\frac{- \frac{π}{2} + 2 \cdot 0 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 0 π}{3})) : 3 - i

Vereinfache

38 (cos (\frac{- \frac{π}{2} + 2 \cdot 1 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 1 π}{3})) : 2 i

Vereinfache

38 (cos (\frac{- \frac{π}{2} + 2 \cdot 2 π}{3}) + i sin (\frac{- \frac{π}{2} + 2 \cdot 2 π}{3})) : - 3 - i

x = 3 - i, x = 2 i, x = - 3 - i

2 x^{3} - 10 x^{2} - 72 x = 0

- 4 x^{3} + 16 x = 0

roo t s x^{4} - 5 x^{2} - 36

x^{3} - 81 = 0

x^{3} - 31 x - 30 = 0