Ako sa vám graf f (x) = x ^ 5 + 3x ^ 2-x pomocou nuly a koniec správania?

Ako sa vám graf f (x) = x ^ 5 + 3x ^ 2-x pomocou nuly a koniec správania?
Anonim

# "Najprv hľadáme nuly" #

# x ^ 5 + 3 x ^ 2 - x = x (x ^ 4 + 3 x - 1) #

# x ^ 4 + 3 x - 1 = (x ^ 2 + a x + b) (x ^ 2 - a x + c) #

# => b + c-a ^ 2 = 0, #

# "" a (c-b) = 3, #

# "" bc = -1 #

# => b + c = a ^ 2, "" c-b = 3 / a #

# => 2c = a ^ 2 + 3 / a, "" 2b = a ^ 2-3 / a #

# => 4bc = a ^ 4 - 9 / a ^ 2 = -4 #

# "Meno k = a²" #

# "Potom dostaneme nasledujúcu kubickú rovnicu" #

# k ^ 3 + 4 k - 9 = 0 #

# "Náhradník k = r p:" #

# r ^ 3 p ^ 3 + 4 r p - 9 = 0 #

# => p ^ 3 + (4 / r ^ 2) p - 9 / r ^ 3 = 0 #

# "Vyberte r tak, aby 4 / r² = 3 => r =" 2 / sqrt (3) #

# "Potom dostaneme" #

# => p ^ 3 + 3 p - (27/8) sqrt (3) = 0 #

# "Náhradník p = t - 1 / t:" #

# => t ^ 3 - 1 / t ^ 3 - (27/8) sqrt (3) = 0 #

# => t ^ 6 - (27/8) sqrt (3) t ^ 3 - 1 = 0 #

# "Substitute u = t³, potom dostaneme kvadratickú rovnicu" #

# => u ^ 2 - (27/8) sqrt (3) u - 1 = 0 #

#disc: 3 * (27/8) ^ 2 + 4 = 2443/64 #

# => u = ((27/8) sqrt (3) pm sqrt (2443) / 8) / 2 #

# => u = (27 sqrt (3) pm sqrt (2443) / 16 #

# "Vezmite riešenie so znakom +:" # #

#u = 6.0120053 #

# => t = 1.8183317 #

# => p = 1.2683771 #

# => k = 1.4645957 #

# => a = 1.2102048 #

# => b = -0.50716177 #

# => c = 1.9717575 #

# x ^ 4 + 3 x - 1 = (x ^ 2 + a x + b) (x ^ 2 - a x + c) #

# "Takže korene sú" #

#x = (-a pm sqrt (a ^ 2-4 * b)) / 2 #

# => x = -0.6051024 pm 0,93451094 #

# => x = -1,53961334 "ALEBO" 0,32940854 #

# "A" #

#x = (a pm sqrt (a ^ 2-4 * c)) / 2 #

# => x = "nie je reálne ako" a ^ 2-4 * c <0 #

# "Takže máme tri nuly pre našu pôvodnú kvintickú rovnicu:" #

#x = = -1,53961334 "ALEBO 0" ALEBO "0.32940854 #

# "Koncové správanie je" #

#lim_ {x -> - oo} = -oo "a" #

#lim_ {x -> + oo} = + oo. "#

# "Takže máme" #

# -oo "………" -1.53961334 "………" 0 "………." 0.32940854 "…….. "+ oo #

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