Answers

2016-02-04T12:20:09+05:30
S₅=S₇
and S₇=S₅+6th term
S₅=S₅+6th term
6th term=0
a+5d=0
2a+10d=0--------eq1
S₁₀=235
n/2(2a+(n-1)d)=235
10/2(2a+9d)=235
2a+9d=47--------eq2
on subtracting eq2 from eq1 we get
d=-47
a=235
S₂₀=20/2(2(235)+19(-47))
S₂₀=10(470-893)
S₂₀=-4230
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