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Question Number 183667 by Mastermind last updated on 28/Dec/22
If w is one of the complex cube   roots of unity, show that  (a+wb+w^2 c)(a+w^2 b+wc) is equal  to (α^2 +b^2 +c^2 −ab−bc−cα).      Kindly help me out, Thank you.
$$\mathrm{If}\:\mathrm{w}\:\mathrm{is}\:\mathrm{one}\:\mathrm{of}\:\mathrm{the}\:\mathrm{complex}\:\mathrm{cube}\: \\ $$$$\mathrm{roots}\:\mathrm{of}\:\mathrm{unity},\:\mathrm{show}\:\mathrm{that} \\ $$$$\left(\mathrm{a}+\mathrm{wb}+\mathrm{w}^{\mathrm{2}} \mathrm{c}\right)\left(\mathrm{a}+\mathrm{w}^{\mathrm{2}} \mathrm{b}+\mathrm{wc}\right)\:\mathrm{is}\:\mathrm{equal} \\ $$$$\mathrm{to}\:\left(\alpha^{\mathrm{2}} +\mathrm{b}^{\mathrm{2}} +\mathrm{c}^{\mathrm{2}} −\mathrm{ab}−\mathrm{bc}−\mathrm{c}\alpha\right). \\ $$$$ \\ $$$$ \\ $$$$\mathrm{Kindly}\:\mathrm{help}\:\mathrm{me}\:\mathrm{out},\:\mathrm{Thank}\:\mathrm{you}. \\ $$
Commented by mr W last updated on 28/Dec/22
if you know (a+b)(c+d), then you can  also solve this.
$${if}\:{you}\:{know}\:\left({a}+{b}\right)\left({c}+{d}\right),\:{then}\:{you}\:{can} \\ $$$${also}\:{solve}\:{this}. \\ $$
Commented by Frix last updated on 28/Dec/22
w^2 =conj w ⇒ w^2 +w=−1  w^3 =1  Should be easy now.
$${w}^{\mathrm{2}} =\mathrm{conj}\:{w}\:\Rightarrow\:{w}^{\mathrm{2}} +{w}=−\mathrm{1} \\ $$$${w}^{\mathrm{3}} =\mathrm{1} \\ $$$$\mathrm{Should}\:\mathrm{be}\:\mathrm{easy}\:\mathrm{now}. \\ $$
Commented by Rasheed.Sindhi last updated on 28/Dec/22
Typos in your question as usual.  Corrected version:  (a+ωb+ω^2 c)(a+ω^2 b+ωc)                =a^2 +b^2 +c^2 −ab−bc−ca
$$\mathcal{T}{ypos}\:{in}\:{your}\:{question}\:{as}\:{usual}. \\ $$$${Corrected}\:{version}: \\ $$$$\left(\mathrm{a}+\omega\mathrm{b}+\omega^{\mathrm{2}} \mathrm{c}\right)\left(\mathrm{a}+\omega^{\mathrm{2}} \mathrm{b}+\omega\mathrm{c}\right) \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:=\mathrm{a}^{\mathrm{2}} +\mathrm{b}^{\mathrm{2}} +\mathrm{c}^{\mathrm{2}} −\mathrm{ab}−\mathrm{bc}−\mathrm{ca} \\ $$
Commented by Mastermind last updated on 28/Dec/22
Thank you sir   but i can′t see the solution
$$\mathrm{Thank}\:\mathrm{you}\:\mathrm{sir}\: \\ $$$$\mathrm{but}\:\mathrm{i}\:\mathrm{can}'\mathrm{t}\:\mathrm{see}\:\mathrm{the}\:\mathrm{solution} \\ $$
Commented by Frix last updated on 28/Dec/22
Maybe the Master of the Mind is not the  Master of the Formulas?
$$\mathrm{Maybe}\:\mathrm{the}\:\mathrm{Master}\:\mathrm{of}\:\mathrm{the}\:\mathrm{Mind}\:\mathrm{is}\:\mathrm{not}\:\mathrm{the} \\ $$$$\mathrm{Master}\:\mathrm{of}\:\mathrm{the}\:\mathrm{Formulas}? \\ $$
Commented by Rasheed.Sindhi last updated on 10/Jan/23
✌️ Share your solution then
Commented by Mastermind last updated on 10/Jan/23
Smile   Anyways, have gotten it BOSS
$$\mathrm{Smile}\: \\ $$$$\mathrm{Anyways},\:\mathrm{have}\:\mathrm{gotten}\:\mathrm{it}\:\mathrm{BOSS} \\ $$
Commented by Mastermind last updated on 19/Jan/23

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