Rozwiąż równania
a)x⁵-2x³+x=0
b)x³+3x²+2x=0
c)x⁴=4x³+5x²
d)6x³+9x²=3x⁴
e)2x⁵=2x⁴+12x³
f)10x⁴+x³=2x²
g)9x⁶+6x⁵+x⁴=0
i)x³+4x=-5x²
j)-½x⁴+x³=½x²
l)16x⁷+8x⁵+x³=0
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a)
x⁵ - 2x³ + x = 0
x·(x⁴ - 2x² + 1) = 0
x·[(x²)² - 2 · x² · 1 + 1²] = 0
x·(x² - 1)² = 0
x·[(x - 1)(x + 1)]² = 0
x·(x - 1)²(x + 1)² = 0
x = 0 ∨ (x - 1)² = 0 ∨ (x + 1)² = 0
x = 0
(x - 1)² = 0
x - 1 = 0
x = 1
(x + 1)² = 0
x + 1 = 0
x = - 1
Odp. x = - 1 lub x = 0 lub x = 1
b)
x³ + 3x² + 2x = 0
x·(x² + 3x + 2) = 0
x = 0 ∨ x² + 3x + 2 = 0
x = 0
x² + 3x + 2 = 0
Δ = 3² - 4 · 1 · 2 = 9 - 8 = 1; √Δ = 1
x₁ = ⁻³⁻¹/₂·₁ = ⁻⁴/₂ = - 2
x₂ = ⁻³⁺¹/₂·₁ = ⁻²/₂ = - 1
Odp. x = - 2 lub x = - 1 lub x = 0
c)
x⁴ = 4x³ + 5x²
x⁴ - 4x³ - 5x² = 0
x²·(x² - 4x - 5) = 0
x² = 0 ∨ x² - 4x - 5 = 0
x² = 0
x = 0
x² - 4x - 5 = 0
Δ = (-4)² - 4 · 1 · (- 5) = 16 + 20 = 36; √Δ = 6
x₁ = ⁴ ⁻ ⁶ / ₂·₁ = ⁻ ²/₂ = - 1
x₂ = ⁴ ⁺ ⁶ / ₂·₁ =¹⁰/₂ = 5
Odp. Odp. x = - 1 lub x = 0 lub x = 5
d)
6x³ + 9x² = 3x⁴
-3x⁴ + 6x³ + 9x² = 0
- 3x²·(x² - 2x - 3) = 0
- 3x² = 0 ∨ x² - 2x - 3 = 0
- 3x² = 0 /:(-3)
x² = 0
x = 0
x² - 2x - 3 = 0
Δ = (- 2)² - 4 · 1 · (- 3) = 4 + 12 = 16; √Δ = 4
x₁ = ² ⁻ ⁴/₂·₁ = ⁻ ²/₂ = - 1
x₂ = ²⁺ ⁴/₂·₁ = ⁶/₂ = 3
Odp. x = - 1 lub x = 0 lub x = 3
e)
2x⁵ = 2x⁴ + 12x³
2x⁵ - 2x⁴ - 12x³ = 0
2x³·(x² - x - 6) = 0
2x³ = 0 ∨ x² - x - 6 = 0
2x³ = 0 /:2
x³ = 0
x = 0
x² - x - 6 = 0
Δ = (- 1)² - 4 · 1 · (- 6) = 1 + 24 = 25; √Δ = 5
x₁ = ¹ ⁻ ⁵/₂·₁ = ⁻ ⁴/₂ = - 2
x₂ = ¹ ⁺ ⁵/₂·₁ = ⁶/₂ = 3
Odp. x = - 2 lub x = 0 lub x = 3
f)
10x⁴ + x³ = 2x²
10x⁴ + x³ - 2x² = 0
x²·(10x² + x - 2) = 0
x² = 0 ∨ 10x² + x - 2 = 0
x² = 0
x = 0
10x² + x - 2 = 0
Δ = 1² - 4 · 10 · (- 2) = 1 + 80 = 81; √Δ = 9
x₁ = ⁻¹ ⁻ ⁹/₂·₁₀ = ⁻ ¹⁰/₂₀ = - ¹/₂
x₂ = ⁻¹ ⁺ ⁹/₂·₁₀ = ⁸/₂₀ = ²/₅
Odp. x = - ¹/₂ lub x = 0 lub x = ²/₅
g)
9x⁶ + 6x⁵ + x⁴ = 0
x⁴·(9x² + 6x + 1) = 0
x⁴·[(3x)² + 2·3x·1 + 1²] = 0
x⁴·(3x + 1)² = 0
x⁴ = 0 ∨ (3x + 1)² = 0
x⁴ = 0
x = 0
(3x + 1)² = 0
3x + 1 = 0
3x = - 1 /:3
x = - ¹/₃
Odp. x = - ¹/₃ lub x = 0
i)
x³ + 4x = - 5x²
x³ + 5x² + 4x = 0
x·(x² + 5x + 4) = 0
x = 0 ∨ x² + 5x + 4 = 0
x = 0
x² + 5x + 4 = 0
Δ = 5² - 4 · 1 · 4 = 25 - 16 = 9; √Δ = 3
x₁ = ⁻⁵ ⁻³/₂·₁ = ⁻ ⁸/₂ = - 4
x₂ = ⁻⁵ ⁺ ³/₂·₁ = ⁻²/₂ = - 1
Odp. x = - 4 lub x = - 1 lub x = 0
j)
-½x⁴ + x³ = ½x²
-½x⁴ + x³ - ½x² = 0 /·(-2)
x⁴ - 2x³ + x² = 0
x²·(x² - 2x + 1) = 0
x²·(x² - 2·x·1 + 1²) = 0
x²·(x - 1)² = 0
x² = 0 ∨ (x - 1)² = 0
x² = 0
x = 0
(x - 1)² = 0
x - 1 = 0
x = 1
Odp. x = 0 lub x = 1
l)
16x⁷ + 8x⁵ + x³ = 0
x³·(16x⁴ + 8x² + 1) = 0
x³·[(4x²)² + 2·4x²·1 + 1²] = 0
x³·(4x² + 1)² = 0
x³ = 0 ∨ (4x² + 1)² = 0
x³ = 0
x = 0
(4x² + 1)² = 0
4x² + 1 = 0
Δ = 0² - 4 · 4 · 1 = 0 - 16 = - 16 < 0
równanie nie ma rozwiązań
Odp. x = 0
* to co jest zapisane w rozwiązaniach kursywą nie trzeba przepisywać - pokazałam jak stosuje się wzór skróconego mnożenia