Write an equation of the line that satisfies the given conditions.?

Question

Through (9,10); undefined slope

I believe i have to put it into point slope form, but i'm not sure because if the slope is indefined, how do I put it into y-y=m(x-x) where m = slope? How do I write an equation for these given conditions?

Answer 1

If you need to put it into point-slope form, you have everything you need. You have a point, and the slope is given. An undefined slope means the line goes up and down. In this case, you can't put it into that form. Since an undefined slope is a x= graph, the x-point is the graph.

x=9

Answer 2

OK, start with the equation:

y = mx + c

Now substitute in (9, 10):

10 = 9m + c

You can rearrange this to get an expression for c (c = ...) or for m (m = ...), which you can then substitute back into your original equation, y = mx + c. Note that this will allow you to get rid of either all the c terms or all the m terms in your original equation, but not both. I think it's probably better to obtain an expression for c from the above, then substitute this back into y = mx + c.

Anyway, nothing too complicated, you just leave the gradient undefined as m.

I don't want to show you the final equation with the substitution, because you'll learn if you do it yourself. But I've told you the simple steps you have to follow.

Hint: your answer should look like this:

y = mx + ...

Where the ... may be a series of numbers/terms, or maybe only one (I'm not telling you which).