To find m,
m= Y2-Y1 / X2-X1
m= 10-5 / 4-2
m= 5/2
m= 2.5
To find b,
Use coordinate (4,10)
y=mx+b
10=2.5(4)+b
10=10+b
b=0
y=2.5x
the answer is y=2.5x
