Summation

[hayleyalissasmith]

Please I need help how do you solve

 

[LCKurtz]

Write the summand as [MATH]3r^2-1[/MATH]. Then look here:

https://byjus.com/maths/sum-of-squares/#:~:text=For%20n%20Natural%20Numbers&text=If%20n%20consecutive%20natural%20numbers,%2B%20n2

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