If the sum of first m terms of AP is n and sum of n terms of AP is m, then show that the sum of (m + n) terms is -(m+n).

Dear sathya ,

 m = n/2[2a + (n-1)d]                                where a and d are the first term and the commom diffrerence 

 n = m/2[2a + (m-1)d]

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

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

now solving the two equations for the 2 values of a and d 

and then put the values of a and d in the equation

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

we will find that is equal to -(m+n)

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?In the 4th step,isnt it 2a + (m-1)d = 2n/m ? If u solve this equations,i dont think we might be gettin the ans.Please show the steps.