For AP show that ap+ap+2q=2ap+q
L.H.S=ap+ap+2q
=[a+(p−1)d]+[a+(p+2q−1)d]
=a+dp−d+a+dp+2dq−d
=2a+2dp−2d+2dq=2(a+dp−d+dq)....(i)
R.H.S
=2ap+q
=2[a+(p+q−1)d]
=[(a+dp+dq−d)]2......(ii)
Hence from (i) and (ii) ,
L.H.S= R.H.S
HENCE PROVED