Find the number of real solutions ( x , y , z ) of
⎩ ⎪ ⎨ ⎪ ⎧ ( x + y ) 3 = z ( y + z ) 3 = x ( z + x ) 3 = y
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This is a cyclic equation. So for solving lets put x=y=z we got (x+x)^3=x means 8x^3 -x=0
Which has three solution
nyc solution....
If we subtract second equation from first we get (x-z)(a^2 +ab+b^2) = z-x, where a = x+y and b = y+z. So, we either have x = z, or a^2 + ab + b^2 = -1, but the latter is not possible, as a^2 + ab + b^2 = (a+b/2)^2 + 3(b^2)/4 > 0. Hence x = z and similarly y = z = x.
TRULY SPEAKING IT WAS MY LUCK WHICH HELPED ME TO GET THE ANSWER CORRECT IN THE SECOND TRIAL.... SO IF ANYONE OF YOU KNOW THE METHOD PLEASE SHARE WITH ALL OF US!!!
calm down...
My was the first trial 😆
My third lol!
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Without loss of generality, lets assume; x>=y>=z. adding x on all 3 sides: 2x>=x+y>=x+z adding y on all 3 sides: x+y>=2y>=y+z. Adding z on all three sides: x+z>=y+z>=2z.
Cubing on all three sides, and substituting for their respective values from the problem statement we get; 8x^3>=z>=y z>=8y^3>=x y>=x>=8z^3
we get z>=y>=x and since we assumed x>=y>=z; the only plausible soln is x=y=z. Substitiuting; we get three solutions..