Given real numbers A and B such that A^2+B^2 = 2 and AB^2+BA^2 = 2, find A and B.
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ab(a+b) = 2
ab = 2/(a+b)
let c = a+b
a^2 + b^2 = 2
(a+b)^2 - 2ab = 2
c^2 - 2(2/c) = 2
c^3 - 4 = 2c
c^3 - 2c - 4 = 0
(c-2)(c^2 + 2c + 2) = 0
c = 2
Reject c^2 + 2c + 2 = 0 because it will give a not real solution:
Therefore:
a+b = 2
ab = 1
Going to:
x^2 - 2x + 1 = 0
(x-1)^2 = 0
x = 1
That means:
So, 1 is the 1st root:
a+b = 2 ----> 1+b = 2 -----. b = 1
Therefore:
a = b = 1