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the sum of terms equidistant from t...

the sum of terms equidistant from the beginning and end in an AP is equal to …………. .

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`T_r=a+(r-1)d`
`r-1,x=n-(r-1)`
`x=n-r+1`
`T_(n-r+1)=a+[n-r+1-1]d=a+(n-r)d`
`T_(rt)T_(n-r+1)=T_1+T_n`
`a+(r-1)d+a+(n-r)d`
`2a+d[r-1+n-r]=2a+[n-1]d`
`T_(rt)+T_(n-r+1)=T_1+T_n=2a+(n-1)d`.
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