Question

find the sum of 51 terms of A.P. in which 2nd and 3rd terms are 14 and 18th respectively ​

Answer 1

Answer:

Step-by-step explanation:

a+2d=14

a+3d=18{change signs while subtracting}

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    d=4

a+2d=14[substitute d=4]

a+2(4)=14

a=14-8

a=6

                 s51=n/2[2a+n-1*d]

                        =51/2[2(6)+{51-1}4]

                          =51/2[212]

                           =51*106

                    s51=5406