Two \(A.P\)’s have the same common difference. The first term of one \(A.P\) is \(2\) and that of the other is \(7\). Show that the difference between their \(10^{th}\) terms is the same as the difference between their \(21^{st}\) terms, which is the same as the difference between any two corresponding terms.
Difference between their corresponding terms \(=\)