CBSE BOARD X, asked by na300, 1 year ago

please solve this question

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Answered by Shushank
1
Sol=3n^+6n
Sn=3n^+6n
formula=an=Sn-Sn-1
an=(3n^+6)-[3(3n-6)(3n+6)^]
an=(3n^+6)-[9n-18)(3n^+2×3n×6+36)]__{a+b^}
an=(3n^+6)-[(9n-18)(3n^+36n+36)]
an=3n^+6-9n+18×3n^-36n-36
9n^-36-45n-18
9n^-45n-54

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