Question

The sum of the series 45²-43²+44²-42²+43²-41²+......upto 30 terms is:

Answer 1

The last 2 terms of series are: (45-15+1)²= 31²  and -(43-15+1)²= -29²
Some of the components of the sum is cleared (from 43² to 31²), and will be following:
45² + 44²  - 30² - 29² = 2220.