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roots of equation x^3+3x^2+3x+3

 Oct 31, 2016
 #1
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Solve for x:
x^3+3 x^2+3 x+3 = 0

Subtract 2 from both sides:
x^3+3 x^2+3 x+1 = -2

Factor x^3+3 x^2+3 x+1 into a perfect cube:
(x+1)^3 = -2

Taking cube roots gives (-2)^(1/3) times the third roots of unity:
x+1 = (-2)^(1/3) or x+1 = -2^(1/3) or x+1 = -((-1)^(2/3) 2^(1/3))

Subtract 1 from both sides:
x = (-2)^(1/3)-1 or x+1 = -2^(1/3) or x+1 = -((-1)^(2/3) 2^(1/3))

Subtract 1 from both sides:
x = (-2)^(1/3)-1 or x = -1-2^(1/3) or x+1 = -((-1)^(2/3) 2^(1/3))

Subtract 1 from both sides:
Answer: |x = (-2)^(1/3)-1     or     x = -1-2^(1/3)     or      x = -1-(-1)^(2/3) 2^(1/3)

 Oct 31, 2016
 #2
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roots of equation x^3+3x^2+3x+3

 

x3+3x2+3x+3=0|x3+3x2+3x+1=(x+1)3(x+1)3+2=0(x+1)3=2x+1=32x=321(1)32=32(cos(π3)+isin(π3))|tanφ=02  φ=π32=32(12+i32)32=3212+i3232x1=321=32121+i3232x1=0.37003947505+i1.09112363597(2)32=32(cos(π3+23π)+isin(π3+23π))32=32(cos(π)+isin(π))32=32(1+i0)32=32x2=321=321x2=2.25992104989(3)32=32(cos(π3+223π)+isin(π3+223π))32=32(cos(53π)+isin(53π))32=32(12i32)32=3212i3232x3=321=32121i3232x3=0.37003947505i1.09112363597

 

 

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 Oct 31, 2016

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