find the sum of first 19 terms of the AP whose sn = 7-4n
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Answered by
2
an=7-4n
Put n=1
a1=7-4*1=3
Put n=2
a2=7-4*2=-1
d=-4
Sn=19/2[2*3+(19-1)-4]
=19/2(6-75)
=19/2*-66
=-627
Put n=1
a1=7-4*1=3
Put n=2
a2=7-4*2=-1
d=-4
Sn=19/2[2*3+(19-1)-4]
=19/2(6-75)
=19/2*-66
=-627
Answered by
0
sn-7-4n the 19 terms of the Ap is 1975
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