Find an equation of the line that passes through the point (-3,-5) and has the same y-intercept as the graph of x+2y=8.

Question

Answers to choose from:

 

1. 2x+y= -11
2. 2x-y= -1
3. 3x+y= -14
4. 3x-y= -4

Answer 1

We are looking for a line that has the same y-intercept (0,y) as the graph of x+2y=8. If you put x =0 into this equation it gives the y-intercept.

0 + 2y = 8

y = 4

y-intercept: (0,4)

The y-intercept is the " b" value in the standard equation for a line;

 

y = mx + b

 

So now we have

 

y = mx + 4

 

We are also given that the line contains the point (-3,-5). Use this to find the slope, m.

You an either plug in the values for x, y or use use the slope formula with the other known point (0,4)

 

m = (4--5)/0--3)

m = (4+5)/(0+3)

m = 9/3

m = 3

 

final equation for the line

 

y = 3x + 4

 

which you can rearrange using algebra to appear as #4

 

y= 3x + 4

-y     

0 = 3x - y + 4

-4

-4 = 3x -y