Sequences & Series
Alternating Sum of Mixed Squares
nta_pyq_2023_apr
Grade 11
Question:
$2\cdot2^2-3^2+2\cdot4^2-5^2+2\cdot6^2-\ldots$ (20 terms) is equal to
Step-by-Step Solution
Key Concept: $\sum_{r=1}^{10}(2(2r)^2-(2r+1)^2)=\sum_{r=1}^{10}(4r^2-4r-1)$.
$1310$.
Correct Answer: 1310