find 'd' if sum of first 'm' term is 'xm^2+ym'?
What a strange problem . . .
Find if sum of first terms is: .
The sum of the first terms is: .
. . where is the first term and is the common difference.
So we have: .
. . which equals: .
Two polynomials are equal if their corresponding coefficients are equal.
. . Hence, we have: .
Without additional information, that's the best we can do.