Question 841761
The big clue is each product is of a form, (a+b)(a-b).  This allows you to take advantage of the difference of squares.


Let me create an example, different from the ones you ask for.


Find 201*205.
Write each factor as a form, (a-b)(a+b).
What number is in the exact middle of 201 and 205?  {{{(201+205)/2=406/2=203}}}.
Use 203 and add something to get 200+w and subtract the same something to get 200-w.  You are creating the expression, using in this case, w=2, to become (203-w)(203+w), specifically {{{(203-2)(203+2)}}}.


You see that you have, according to the difference of squares formula, 
{{{highlight_green(201*205=(203-2)(203+2)=203^2-2^2)}}}, which you should be able to compute fast.