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From elementary calculus I was met with the following problem, and I am interested if my answer is correct. The problem is to find the slopes and $y$-intercepts of the following lines:

1) $x=-2$


2) $y=-1$.

I know that for the $y$-intercept we should set $x$ equal to zero and solve for $y$. For example, the $y$ intercept for $y=2x+3$ is $(0,3)$ and slope is $2$. For the first equation, which is a line parallel to the $y$-axis and never crosses it, I think the $y$-intercept is undefined (or maybe zero) and also the slope is the same.

But for the second equation, the $y$-intercept is $-1$ (because it crosses $y$ at $-1$ point for all values of $x$). But I think that the slope is undefined. I think this because if we compare $y=-1$ to $y=mx+b$ (where $m$ is the slope), then we can't determine a simple slope.

Please help me. Am I wrong with my thinking or not?

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$y=-1$ can be written $y=0\cdot x-1$. So the slope for 2) is 0. The rest of your reasoning seems on track. – David Mitra Nov 16 '11 at 10:25
up vote 1 down vote accepted

For the first one $x=-2$ the slope is infinite and there is no $y$-intercept. For the second one $y=-1$ the slope is $0$ and the $y$-intercept is $(0,-1)$.

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thanks guys i have missed some logic here thanks for explanation – dato datuashvili Nov 16 '11 at 10:35

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