Question

A line passes through (-1, 7) and (2, 10).

Which answer is the equation of the line?

a. -x+y=12
b. -3x+y=4
c. -3x + y = 16
d. -x+y=8

Answer 1

d. -x + y = 8

Explanation:

First find the rate of change [slope]:

-y₁ + y₂\-x₁ + x₂ = m

`(-7 + 10)/(1 + 2) = (3)/(3) = 1`

Then, we can go ahead and use the Slope-Intercept Formula instead of the Point-Slope Formula because you get it done swifter. It does not matter which ordered pair you choose:

10 = 1[2] + b

2

8 = b

y = x + 8 >> Line in Slope-Intercept Form

Since the exercise wants the equation in Standard Form:

y = x + 8

-x -x

________

-x + y = 8 >> Line in Standard Form

__________________________________________________________

7 = 1[-1] + b

-1

8 = b

y = x + 8 >> Line in Slope-Intercept Form

y = x + 8

-x -x

________

-x + y = 8 >> Line in Standard Form

** You see? I told you it did not matter which ordered pair you chose because you will always get the exact same result, plus the fact that I told you it was alot swifter than the Point-Slope Formula.

* Tip: Use the Point-Slope Formula when it tells you to, otherwise keep using the Slope-Intercept Formula. That way, you get your work done in a jip!

I am joyous to assist you anytime.