Question

What is the equation of this line in standard form?

A: 9x−8y=23

B: 8x−9y=23

C: 8x−9y=−23

D: 8x−7y=−25

Answer 1

B:8x-9y=23

Explanation:

First find the slope:

m= y2-y1/x2-x1

y2 is 3

y1 is -1

x2 is 1/2

x1 is -4

3-(-1) is 4

1/2-(-4) is 9/2

Now the equation looks likes this:

4 / 9/2

Which can be rewritten as

4*2/9

Thus the slope is 8/9

So the equation is

y=8/9x+b

Now you can substitute to find the y-intercept:

(you can do either (-4,1) or (1/2,3)

I am going to do (1/2,3) since it is easier

3=8/9(1/2)+b

Simplify:

3=4/9+b

Subtract 4/9 on both sides:

b=23/9

Thus the equation is

y=8/9x+23/9

Multiply 9 on both sides:

9y=8x+23

Subtract 8x on both sides:

8x-9y=23

Hope this helps!