Question

The first term of an A.P. is 25 Find the Sum of its 41stfirst terms & D2​

Answer 1

Answer:

1025

Step-by-step explanation:

$a21 = a + 20d \\ 25 = a + 20d \\ a = 25 - 20d \\ \\ than \\ s41 = 41 \div 2(2(25 - 20d) + 40d) \\ 41 \div 2(2(25 - 20d) + 2(20d) \\ 41 \div 2 \times 2(25 - 20d + 20d) \\ = 41(25) \\ \\ = 1025$