A line intersects the points (-8,-1) and (1,8) . What is the slope-intercept equation for this line?

Answer 1

Another way to solve is to use...

y - y₁ = m(x - x₁)

Jackson showed you how to find m, the slope. Either point can be (x₁,y₁). I'll use the second.

y - 8 = 1(x - 1)

y - 8 = x - 1

y = x + 7

You decide which works best for you!

Answer 2

The slope, 'm', can be determined from the following equation: m = (y₂-y₁)/(x₂-x₁) where x_{1 and} y₁ are one of the pairs of given coordinates and x₂ and y₂ are the other pair (it doesn't matter which pair you call 1 and which you call 2).

This gives us: m = (8 - (-1))/(1 - (-8)) = 10/10 = 1

The slope is 1, and we can put this into our slope-intercept form of the equation for a liner which is y = mx + b where m is the slope (which equals 1) and b is the y-intercept (which we need to find). We will use one of the points we were given in the question and plug those in for x and y (we'll use (1,8) since positive numbers are easier to handle):

y = mx + b

8 = 1(1) + b

8 = 1 + b

b = 7

Now we have our slope (m = 1) and y-intercept (b = 7) and can plug those in to the equation for a line:

y = 1x + 7 or y = x + 7