...of a straight line that passes through the points (1,5) and (7, -1).

Here's my answer, is this correct? or is their an easier method?

Y1 - Y2 / X1 - X2

5 - (-1) / 1 - 7

6 / -6

Knowing the formula y=mx+b and m slope to be = -1 , we can plug back in:

5 = (-1) 1 + b

5 = -1 + b

5 - (-1) = b

6 = b

y = (-1)x + b