Writing an algebraic expression. When two binomials differ only by the sign between their terms one a plus the other a minus we call this a Difference of Two Squares. Well doubling your penny could be expressed as 2d where d equals the amount of days you have been doubling.
Here is a list of Algebraic formulas a 2 b 2 a ba b a b 2 a 2 2ab b 2.
Writing an algebraic expression. 1 4 9 16 25 36 49. So its about 145 doublings. Doubling just once you get 2 c.