how do you write an equation of the line with the slope of -2 and containing the point (2,-4)?

Question

tkhunny · Answer

A line in slope-intercept form looks like this...

y = mx + b

We are given the slope.  -2  Now, it looks like this...

y = -2x + b

We are given a point.  (2,-4).  What do you suppose we could do with that information?

anonymous · Answer

well i know that is going to be the y intercept and it the point was (0,-4) the y intercept would be -4 but since there is now a 2 instead of a 0 i have no idea what to do.

tkhunny · Answer

Not bad.  Just substitute, anyway.

y = -2x + b

(2,-4) suggests x = 2 when y = -4, so

-4 = -2(2) + b

And we should be able to solve this for 'b'.  No?

anonymous · Answer

so b would equal 0?

tkhunny · Answer

Looks like it.  Good work.

anonymous · Answer

hey thanks i appreciate it!