Answers

2015-01-17T20:23:38+05:30
LET a BE THE FIRST TERM AND d BE THE COMMON DIFFERENCE.
 NOW SX/SKX=X/2 (2a + (X-1)d)/KX/2(2a + (KX - 1)d)
                      =(2a + XD- D)/(2AK + K
²XD - KD) 
                      =
(2a + XD- D)/((2A-D)K + K²XD)

NOW SINCE SX/SKX IS INDEPENDENT OF X THEN,
(2A - D )K=0 D=2A.. HENCE PROVED

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