Question

find the sum of first four terms of AP with general term tn=(5-2n)​

Answer 1

$t_{n} = 5 - 2n \\ \\ t_{1} = 5 - 2(1) = 3 \\ t_{2} = 5 - 2(2) = 1 \\ t_{3} = 5 - 2(3) = - 1 \\ t_{4} = 5 - 2(4) = - 3$

Hence, sum of the first four terms

= 3 + 1 + (-1) + (-3)

= 3 + 1 - 1 - 3

= 0