SOLUTION: The sum of the first and last terms of a linear sequence is 42. If the sum of all the terms is 420 and the second term is 4, find

Use this formula for the sum of arithmetic progression:

 = . 

(see the lesson Arithmetic progressions in this site).

Then you get 

 =   --->   n = 20.

Next, from the condition you have these two equations

 +  = 42,
 = ,

or

 +  = ,
 = ,

or

 +  = ,
 = .

The solution of this system is  = 2, d = 2.

Get it by any method.

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Do not use the term "a linear sequence".


Use the commonly accepted term "arithmetic progression".