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How can we prove/disprove if $W=V(x^{2}+x)$ and $T=V(xy)$ ,both subsets of $\mathbb{A}^{2}$, are isomorphic algebraic sets?

At first I wanted to use Corollary $3.7$ page $20$ of Hartshorne's book:

If $X$ and $Y$ are two affine varieties then $X \cong Y$ if and only if $A(X) \cong A(Y)$.

I think $A(W) \cong k[y] \times k[y]$. But we can't use the above result because none are affine varieties, they are clearly reducible.

Any hint? (this is before the chapter about projective varieties).

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    They are not isomorphic since $T=V(xy)$ is connected while $W=V(x^{2}+x)$ is not.2012-03-25

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Note that both $W$ and $T$ have two irreducible components. Suppose we had some isomorphism between $T$ and $W$. Any irreducible component of $T$ must be mapped to a irreducible component of $W$, as closed sets are preserved by isomorphisms. But the irreducible components of $W$ are disjoint, while those of $T$ are not, so this means the point $(0,0)$ which lies in the intersection of the two irreducible components of $T$ is mapped to two points. Clearly this is impossible, so $T$ and $W$ are not isomorphic.