SOLUTION: The sum of the 1st and 2nd terms of an AP is 4 and the 10th term is 19 Find d sum of the 5th and 6th terms

 = 1;

 = 3;

d = 2 (the common difference);


Check:   =  + d*(10-1) = 1 + 2*9 = 19  ! Correct !


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 = 1 + 4*2 = 9;

 = 1 + 5*2 = 11;

 +  = 9 + 11 = 20.

 +  = 4,      (1)
 =  = 19,   (2)

which gives you the system of two equations in two unknowns

 = 4,
 = 19,


You can solve it by any method you know/you want to get the same answer.