The required equation is y = x + 2
Solution:
Given three points are (1,3) (3,5) (5,7)
A quadratic equation for three points is given by

Assume the point 1,3 and substitute in (1)

Let us substitute 3,5 in (1)
Let us substitute 5,7 in (1)
Subtracting 2 and 3



Subtracting 4 and 3

Substituting b in 5,





Substituting a, b, c in 1 we get the quadratic equation
