Heat equation solving quadratic equation with complex numbers

dp182
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Homework Statement


given that kλ2-ρcpuλ-ρcpωi=0
plug into the quadratic formula and get out an equation that looks like this

λ=α+iβ±γ√(1+iδ) where α,β,γ,and δ are in terms of ρ,cp,u,k, and ω

Homework Equations


(-b±√b2-4ac)/2a
2-ρcpuλ-ρcpωi=0
λ=α+iβ±γ√(1+iδ)

The Attempt at a Solution


so I plugged it in and came out with
(ρcpu/2k)±(ρcpu/2k)√1+(4kωi/ρcpu2)
so γ=(ρcpu/2k) and δ=(4kω/ρcpu2)
but I'm unable to make the first term α+iβ and help would be great
 
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dp182 said:

Homework Statement


given that kλ2-ρcpuλ-ρcpωi=0
plug into the quadratic formula and get out an equation that looks like this

λ=α+iβ±γ√(1+iδ) where α,β,γ,and δ are in terms of ρ,cp,u,k, and ω

Homework Equations


(-b±√b2-4ac)/2a
2-ρcpuλ-ρcpωi=0
λ=α+iβ±γ√(1+iδ)

The Attempt at a Solution


so I plugged it in and came out with
(ρcpu/2k)±(ρcpu/2k)√1+(4kωi/ρcpu2)
Should be λ= (ρcpu/2k)±(ρcpu/2k)√1+(4kωi/ρcpu2) since you are solving the quadratic equation for λ. Note that I didn't check your work.

dp182 said:
so γ=(ρcpu/2k) and δ=(4kω/ρcpu2)
but I'm unable to make the first term α+iβ and help would be great

They're not asking you to make the first term α+iβ, just that you have an equation that has the form they give. In what you have, α = ρcpu/(2k) and β = 0.
 
There are two things I don't understand about this problem. First, when finding the nth root of a number, there should in theory be n solutions. However, the formula produces n+1 roots. Here is how. The first root is simply ##\left(r\right)^{\left(\frac{1}{n}\right)}##. Then you multiply this first root by n additional expressions given by the formula, as you go through k=0,1,...n-1. So you end up with n+1 roots, which cannot be correct. Let me illustrate what I mean. For this...
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