Question

How to write the slope-intercept form of the equation of the line through the given points: (-1,-3) and (-4,5)

Answer 1

You can use the formula: y=mx+b; where m=slope and y=y-intercept.

1.) To find the slope: use the formula y1-y2/x1-x2, thus 5-(-3)/(-4)-(-1). The slope is -8/3.
2.) Solve using proportions: slope=y1-y2/x1-x2
therefore: -8/3=(y-(-3))/(x-(-1))=
3y+9=8x-8
3.) Isolate the y variable by subtracting the 9 from both sides and dividing by three: y=(-8/3)x-(17/3)

Answer 2

The slope-intercept form of a line is:

y=mx+b, where m=slope and b=y-intercept (value of y when x=0)

First you must find the slope, or m value.

m=(y2-y1)/(x2-x1), which is the change in y divided by the change in x. In this case:

m=(5--3)/(-4--1)

m=(5+3)/(-4+1)

m=8/-3

m=-8/3

So far our line is:

y=-8x/3+b, we can now solve for the y-intercept, or b, using any point on the line, I'll use (-4,5):

5=-8(-4)/3+b

5=32/3+b

15/3=32/3+b

15/3-32/3=b

-17/3=b

So now we know the value for both terms in our line:

y=(-8x-17)/3