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Answers
Given : x³ - 3x + 1 = 0 has roots α , β and γ
To Find : Cubic equation with roots α² , β² and γ²
Solution:
x³ - 3x + 1 = 0 has roots α , β and γ
α + β + γ = 0 as no coefficient of x²
αβ + βγ + αγ = - 3
αβγ = - 1
α² + β² + γ² = (α + β + γ )² - 2(αβ + βγ + αγ)
= 0 - 2(-3)
= 6
α² β² + β² γ² + α² γ² = ?
αβ + βγ + αγ = - 3
Squaring both sides
=>α² β² + β² γ² + α² γ² + 2αβγ( α + β + γ ) = 9
=> α² β² + β² γ² + α² γ² + 0 = 0
=> α² β² + β² γ² + α² γ² = 9
α² β² γ² = (αβγ )² = 1
α² + β² + γ² = 6
α² β² + β² γ² + α² γ² = 9
α² β² γ² = 1
x³ - 6x² + 9x - 1 = 0
x³ - 6x² +9x - 1 = 0 is the required equation
And very simple solution by @pulakmath007 in attachment :
https://brainly.in/profile/pulakmath007-13087864
its given α , β , γ are roots and α² , β² , γ² are roots of new
so just replace x with √x in x³ - 3x + 1 = 0
=> (√x)³ - 3√x + 1 = 0
=> x√x - 3√x = - 1
=> √x(x - 3) = - 1
Squaring both sides
=> x(x - 3)² = 1
=> x( x² - 6x + 9) = 1
=> x³ - 6x² + 9x - 1 = 0
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Given :- The equation x³ - 3x + 1 = 0 has roots a, b and c. Find a cubic equation with integers coefficients that has roots a², b² and c² ? { I am assuming alpha as a , beta as b and gama as c .}
Solution :-
we know that, for the cubic equation P(x) =ax³ + bx² + cx + d = 0 ,a ≠ 0.
- If α, β and γ are zeros of P(x),
Then :-
⟿ α + β + γ = (-b)/a
⟿ αβ + βγ + αγ = c/a
⟿ αβγ = (-d)/a
comparing given cubic equation x³ - 3x + 1 = 0 with ax³ + bx² + cx + d = 0 , we get,
- a = 1
- b = 0
- c = (-3)
- d = 1
then,
→ a + b + c = 0
→ ab + bc + ca = (-3)
→ abc = -1
so,
→ (a + b + c) = a² + b² + c² + 2(ab + bc + ca)
→ 0 = a² + b² + c² + 2 * (-3)
→ a² + b² + c² = 6
and,
→ (abc)² = (-1)²
→ a²b²c² = 1
and,
→ (ab + bc + ca)² = a²b² + b²c² + c²a² + 2(ab²c + bc²a + ca²b) = a²b² + b²c² + c²a² + 2abc(a + b + c)
→ (-3)² = a²b² + b²c² + c²a² + 2 * (-1) * 0
→ a²b² + b²c² + c²a² = 9
comparing again,
→ a² + b² + c² = sum of roots = -b/a = 6
- b = (-6)
- a = 1
and,
→ a²b²c² = product of roots = -d/a = 1
- d = (-1)
- a = 1
and,
→ a²b² + b²c² + ²a² = c/a = 9
- c = 9
- a = 1
therefore, required cubic equation, whose roots are a², b² and c² will be ,
→ ax³ + bx² + cx + d = 0
→ x³ - 6x² + 9x - 1 = 0
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Let a, b and c be non-zero real numbers satisfying (a³)/(b³ + c³) + (b³)/(c³ + a³) + (c³)/(a³ + b³)
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if a²+ab+b²=25
b²+bc+c²=49
c²+ca+a²=64
Then, find the value of
(a+b+c)² - 100 = __
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