I hope we all remember the square formula : (a + b)2 = a2 + b2 +2ab
Step 1 : Break the number such that a=5, and b=6
Step 2 : Compute a2, ab and b2 and write as shown in the updated formula
Step 3 : Notice the second row of the formula is obtained by just repeating the middle term ab of the first row.
If ab and b2 are more than 1 digit add the carry to left part leaving 1st digit in their places.