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| 1. |
Sum of m terms =n and sum of n terms =m then prove that sum of m+n terms = -(m+n) |
| Answer» m=n/2(2a+(n-1)d) by solving this we get 2m=2an+dn^2-dn --------(1) then by same method 2n=2am+dm^2-dm------(2) from equation 1and 2 we get -2=2a+d(m+n)-1). Now s(m+n)=m+n/2(2a+(m+n)d ) now by equation 3 s(m+n)=-(m+n) hence proved | |