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Reals of Symmetric Equations (Posted on 2024-09-11) Difficulty: 3 of 5
a4+8b=4a3-4-16√3
b4+8a=4b3-4+16√3

If a, b are real numbers, then find the value of a4+b4.

No Solution Yet Submitted by Danish Ahmed Khan    
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solution by graphing Comment 1 of 1
A graph (a,b) shows the two equations appear to have one point in common: (1+sqrt3 ,1-sqrt3) from which a^4+b^4 = 56

https://www.desmos.com/calculator/l0nucubtco

If you add the equations together you can rearrange the result as

a^4-4a^3+8a+4 = -(b^4-4b^4+8b+4)

whose graph is just four dots: (1+/+/-/-sqrt3 , 1+/-/+/-sqrt3)

Subtracting the two equations gives a sextic curve that goes through the right one.

Guessing the equality (from adding) works when both sides are zero we can graph the quartic a^4-4a^3+8a+4 which has two double roots at 1+/=sqrt3.






  Posted by Jer on 2024-09-15 19:52:59
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