Question

A.P QUESTION SOLVE FOR THE BRILLIANT ​

Answer 1

Step-by-step explanation:

given, Sm=Sn

m/2[2a+(m-1)d]=n/2[2a+(n-1)d]

2am+m²d-md=2an+n²d-nd

2a(m-n)+d{m²-m-n²+n}=0

2a(m-n)+d{(m²-n²)-(m-n)}=0

2a(m-n)+d{(m-n)(m+n)-(m-n)}=0

(m-n){2a+d(m+n-1)}=0

therefor, 2a+(m+n-1)d=0

d=-2a/(m+n-1)

Sm+n=m+n/2[2a+(m+n-1)d]

=m+n/2[2a+(m+n-1)(-2a/m+n-1)]

=m+n/2[2a-2a]

=m+n/2 ×0

=0