algebra problem plz help

Hello, Debasish!

If x2+y2+2x+1=0\displaystyle \text{If }x^2+y^2+2x+1\,=\,0
. . find the value of: x31+y35\displaystyle \text{find the value of: }\:x^{31}+y^{35}

We have: .x2+2x+1+y2=0(x+1)2+y2=0\displaystyle x^2+2x+1 + y^2 \:=\:0 \quad\Rightarrow\quad (x+1)^2 + y^2 \:=\:0

. . Hence: .x=-1,y=0\displaystyle x = \text{-}1,\:y = 0


Therefore: .x31+y35  =  (-1)31+(0)35  =  1+0  =  1\displaystyle x^{31} + y^{35} \;=\;(\text{-}1)^{31} + (0)^{35} \;=\;-1 + 0 \;=\;-1
 
I want to add a little explanation to Soroban's elegant solution.

(x+1)2 and y2 will be always positive - because those are square numbers.

Sum of two positive numbers can be equal to zero - iff each number is equal zero.

Then rest of the story....
 
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