Write an expression for the slope of a line passing through the points (0,-3) and (x,-9). What values of x will produce a positive slope? What values of x will produce a negative slope? What value of x will produce a vertical line? Can a horizontal line be formed from these two points? Why or why not?

Question

Write an expression for the slope of a line passing through the points (0,-3) and (x,-9).  What values of x will produce a positive slope?  What values of x will produce a negative slope?  What value of x will produce a vertical line?  Can a horizontal line be formed from these two points?  Why or why not?

amistre64 · Answer

x < 0 would make a positive slope; at x = 0 we have an undefined slope

amistre64 · Answer

x = (-inf,0) produces a positive slope

x = (0,inf) makes it a negative slope;

and at x=0 we get a vertical line that is undefined

anonymous · Answer

So what will the expression be for the first part of the problem?

amistre64 · Answer

what do you mean?

anonymous · Answer

Well, I'm thinking I have to put this into a formula like the "two point formula" since I was given two points.  No?

amistre64 · Answer

the slope formula for these to points as is:

-9+3
----- = m
 x - 0

amistre64 · Answer

or simply:

-6
--- = m
  x

anonymous · Answer

Or maybe this one:  y=mx + b?

amistre64 · Answer

y+3      -6
---- = ---
x-0        x

y+3 = (-6/x)(x-0)

y = -9 is what they tunrs out to, but I dont think that is right