Question

Which equation of a line passes through the points (3, −1) and (6, 1)?

Answer 1

Answer:

Y = 2/3x - 3

Step-by-step explanation:

Recall the general equation for a straight line is

y = mx + b

where m is the gradient and b is the y-intercept

given 2 points whose coordinates are (x1, y1) and (x2, y2), m can be found with the following formula:

m = $\frac{y1-y2}{x1-x2}$

in this case, x1 = 3, y1 = -1, x2 = 6, y2=1

applying these values to the formula for m will give

m =  (-1 -1) / (3-6) = 2/3

We can see immediately that only the first (top-most) answer has this value for m and we can guess that this is probably the answer.

But we can still check to confirm:

If we substitute this back into the general equation, we get:

y = (2/3)x + b

In order to find the value for b, we substitute any one of the 2 given points back into this equation. Lets choose (6,1)

1 = (2/3)(6) + b

1 = 4 + b

b = -3

Confirm  Y = 2/3x - 3 is the answer.