Math
posted by Jon on .
Write an equation in slopeintercept form for the line that passes through (3,5) and (2,1).
y2y1/x2x1
15/23
4/5= slope
y=mx+b
y=4/5(3)+b
2=2.4+b
4.4= yintercept
y= 4/5x+4.4 (answer)

Rewrite the slope as m = 4/5. 4/5 is the same thing but looks awkward.
y = (4/5) x + b
5 = [(4/5)*3] + b
5 = 12/5 + b
b = 13/5
y = (4/5)x + 13/5 
Ok, we lmow that the slope is 4/5.
y=mx+b
y=4/5(3)+b
2=2.4+b
subtract 2.4 from both sides
4.4 which is how I got the yintercept
y= 4/5x+4.4
13/5 = 2.6 not 4.4 
In solving for b, you took the xvalue from one point (x=3) and, for y, you used the x value from the other point (x=2) instead of y. You should have used y=5, as I did in my derivation. You have to use the x and y values of one known point to get the line to pass though that point.