Question

Find the equation of the line that passes through the points
(2, 4) and (4, 2).

Answer 1

first we need to find the slope by using the slope formula.
slope(m) = (y2 - y1) / (x2 - x1)
(2,4) x1 = 2 and y1 = 4
(4,2) x2 = 4 and y2 = 2

now sub in our info...
m = (2 - 4) / (4 - 2)
m = -2/2
m = -1 <-- your slope

you with me so far ?

Answer 2

Now that we know the slope, and we have points, we can use the point slope formula.
y - y1 = m(x - x1)
m (slope) = -1
and we can use either of the points, I will use (2,4)
(2,4) x1 = 2 and y1 = 4

now we will sub
y - 4 = -1(x - 2)
y - 4 = -x + 2
y = -x + 2 + 4
y = -x + 6 <-- your answer

any questions ?