- #1
DorelXD
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Homework Statement
Let [itex] a,b,c,d [/itex] be real number that satisfy the property that [itex] a + b = c + d [/itex] and [itex] a^2 + b^2 = c^2 + d^2 [/itex]. Show that [itex] a^n + b^n = c^n + d^n [/itex] for any [itex] n [/itex], a natural number ( with [itex] n > 0 [/itex] ) .
Homework Equations
[tex] x^n - y^n = (x-y)(x^{n-1} + x^{n-2}y + x^{n-3}y^2 + ... + x^1y^{n-2} + y^{n-1}) [/tex]
The Attempt at a Solution
I have two ideas but I couldn't succed to apply them properly:
1) First, I'm thinking at a mathematical induction, but it seems that in this case the proof via induction isn't so straightforward.
2) Second, I'm thinking of writing that : [itex] a^n - c^n = d^n - b^n [/itex] and, then then using the formula:
[tex] x^n - y^n = (x-y)(x^{n-1} + x^{n-2}y + x^{n-3}y^2 + ... + x^1y^{n-2} + y^{n-1}) [/tex]
But this dosen't seem very helpful either. The very first move I thought of making is writing that:
[itex] a^n - c^n = d^n - b^n \to (a-c)(... )= (d-b)(...) [/itex] and get rid of the first paranthesis. Unfortunately, I cannot do this because I don't know for sure if (a-c) and (d-b) are diffrent from 0.
Please, can sombeody guide me to the solution ? Are my ideas good ?