Question

Find the common difference for an A.P. whose first term is
5 and the sum of first four term
is half the sum of the next four term .​

Answer 1

Answer:

d =  2                                                                         (。_。)

Step-by-step explanation:

a = 5

S4 = 1/2(S8 - S4)

=> n/2 [ 2 a+(n-1)d  ] =  1/2{ n'/2[   2 a+(n'-1)d  ] - n/2[  2 a+(n-1)d  ]}

=> 2 [2(5) + 3d]  = 1/2 { 8/2[2(5)+7d ] - 2 [2(5) + 3d]}

=> 20 + 6d = 1/2{40 + 28d - 20 - 6d}

=> 20 + 6d = 20 + 14d - 10 - 3d

=> 6d - 14d + 3d = -10

=> -5d = -10

=> d = 2

I hope u find it useful.                  (°ー°〃)