Proving that this function is not injective

by Archimedess   Last Updated October 01, 2019 20:20 PM - source

Let $f:\mathbb{R}^2\to\mathbb{R}^2$ given by $f(x,y)=((x+2)^2+y, 2x-3y-1)$

how do I prove that this function is not injective and thus not globally invertible?

I tried with $f(x,y)=f(u,v)$ but the system is quite impossible/hard for me.. is there another way?

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