Formula

A man is 40 years old.Let us find a formula giving his age before or after any number of years.
The present age of the man is 40 years.
After 5 years ,he will therefore be 40+ 5 years old.
After 7 years, he will therefore be 40+7 years old.
After 8 years, he will therefore be 40+8 years old.
After x years, he will therefore be 40+x years old.

Again 8 years ago the man was 40-8 years old.
Again 10 years ago the man was 40-10 years old.
Again 12 years ago the man was 40-12 years old.
Again y years ago the man was 40-y years old.

From ( 40 + x) we can find out the man's age after any number of years by giving any value to x
 in ( 40 + x).Thus after 15 years the man will be 40+15=55 yeras old.

Similarly from ( 40 - y ) we can get his age before any number of years by giving any value to y in
( 40 - y).Thus 12 years before the an was 40-12= 28 yeras old.

Hence we can derive a formula from such statements.Algebra has a wider scope and how the use of letters for numbers helps us to make general statements leading to formulae.

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