Some equations involving $x$ and $y$ define $y$ as a function of $x$, and others do not. For example, if $x+y=1$ we can solve for $y$ and obtain $y = 1-x$ and we can then think of $y = f(x) = 1-x$. On the other hand, if we have the equation $x=y^2$ then $y$ is not a function of $x$ since for a given non-negative value of $x$ the value of $y$ could equal the positive or the negative square root of $x$. Indicate by True (T) or False (F). whether the following equations define $y$ as a function of $x$. You may assume that $0 \leq x \leq 1.$
1. $y^2 + x = 1$
2. $y + x^2 = 1$
3. $y - |x| = 0$
4. $x+y = 1$
5. $y^2 + x^2 = 1$
6. $2 x + 6 y + 2 = 0$
7. $|y| - x = 0$