Odpowiedzi

2010-02-02T13:58:06+01:00
(n-1)n/(n+5)(n+6)<1/2/*(N+5)(N+6)
(n-1)n<1/2(n+5)(n+6)
n²-n<1/2(n²+11n+30)
n²-n<1/2n²+11/2n+15
1/2n²-13/2n-15<0/(-2)

-n²+13+30>0
Δ=169+120=289
√Δ=17
n=-13-17/-2=15
n=-13+17/-2=-2
2010-02-02T14:05:13+01:00
(n-1)n/(n+5)(n+6)<1/2
(n-1)n/n²+6n+5n+30 <1/2 /×(n²+6n+5n+30)
n(n-1) < 1/2×(n²+6n+5n+30)
n²-n < 1/2n²+11/2n+15
n²-1/2n²-n-11/2n-15 < 0
1/2n²-13/2n-15 < 0 /×2
n²-13-30<0

a=1
b=-13
c=-30

Δ=b²-4ac
Δ=-13²-4×1×(-30)
Δ=169+120
Δ=289

n₁=-b-√Δ /2a
n₂=-b+√Δ /2a

n₁=13-17 /2
n₂=13+17 /2

n₁=-2
n₂=15