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Write the equation of a line that has a y-intercept of 3 and passes through the point (2,-4).

 

We just recently went over this in class, but I've forgotten and need a review.

 Nov 15, 2014

Best Answer 

 #1
avatar+128448 
+10

A y intercept of 3 means the point (0, 3)...

Now note something.......we could find the slope arithmetically, but think about this....from (0,3) to (2, -4)...y changes by -7 and x changes by 2......and that's the definition of the slope....so...our slope is -7 / 2 

Now....using the point slope form, we have

y - y1 = m(x - x1)     where m is the slope and (x1, y1) is a point on the line....(let's use (0, 3))

So we have

y - 3 = (-7/2)(x - 0)

y - 3 = (-7/2)x      add 3 to both sides

y = (-7/2)x + 3

And there you go !!!

 

 Nov 15, 2014
 #1
avatar+128448 
+10
Best Answer

A y intercept of 3 means the point (0, 3)...

Now note something.......we could find the slope arithmetically, but think about this....from (0,3) to (2, -4)...y changes by -7 and x changes by 2......and that's the definition of the slope....so...our slope is -7 / 2 

Now....using the point slope form, we have

y - y1 = m(x - x1)     where m is the slope and (x1, y1) is a point on the line....(let's use (0, 3))

So we have

y - 3 = (-7/2)(x - 0)

y - 3 = (-7/2)x      add 3 to both sides

y = (-7/2)x + 3

And there you go !!!

 

CPhill Nov 15, 2014
 #2
avatar+1090 
0

Thanks...just missing  "A y intercept of 3 means the point (0. 3)...". That is very helpful.

 Nov 15, 2014

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