Odpowiedzi

2010-03-14T20:30:11+01:00
1.
-20x²-x+1>0
a= -20
b= -1
c= 1
Δ=b²-4ac
Δ= (-1)²-4*(-20)*1
Δ= 1+80
Δ= 81
√Δ=9
x1= -b-√Δ/2a=1-9/-40= -8/-40=5
x2= -b+√Δ/2a=1+9/-40= 10/-40= -4

2.
x³+5x²-9x-45=0
x²(x+5)-9(x+5)=0
(x²-9)(x+5)=0
(x-3)(x+3)(x+5)=0

x-3=0
x=3

x+3=0
x=-3

x+5=0
x=-5