sathee Ask SATHEE

Welcome to SATHEE !
Select from 'Menu' to explore our services, or ask SATHEE to get started. Let's embark on this journey of growth together! 🌐📚🚀🎓

I'm relatively new and can sometimes make mistakes.
If you notice any error, such as an incorrect solution, please use the thumbs down icon to aid my learning.
To begin your journey now, click on

Please select your preferred language

JEE PYQ: Sequence And Series Question 42

Question 42 - 2020 (08 Jan Shift 2)

The sum, $\sum_{n=1}^{7}\frac{n(n+1)(2n+1)}{4}$ is equal to _______.

Show Answer

Answer: (504)

Solution

$= \frac{1}{4} \cdot \frac{7}{8}\sum_{n=1}^{7}(2n^3 + 3n^2 + n)$

$= \frac{1}{4}\left[2\left(\frac{7.8}{2}\right)^2 + 3\left(\frac{7.8.15}{6}\right) + \frac{7.8}{2}\right]$

$\Rightarrow \frac{1}{4}[1568 + 420 + 28] = \frac{1}{4}[2016] = 504$


Learning Progress: Step 42 of 70 in this series