find m and b using the equation for line AB

"m" will be the slope.......

We can find it thusly.....

[ subtract the y coordinates in some order ]  /  [ subtract the x coordinates in the same order ]   

So we have

[ 5 - 2  ]  / [ 1 - 6]  =  [ 3] / [ -5]  =     -3/5       and this is the slope of AB

"b"  will be the y intercept........we need to get to this form  →  y  = mx + b

Using either one of the points and the slope, we can write

y  = -(3/5) ( x - 1) + 5    simplify

y = (-3/5)x +  3/5  + 5         →     "5"  can  be writen as  25/5 .....

So.....we have

y = (-3/5)x  +  3/5 + 25/5

y = (-3/5)x   +  28/5

So......  (-3/5)  = m    and   28/5  = b

Hope that helps  !!