Question

Find the 15th term of the AP –40, –15, 10, 35,....

Answer 1

The given AP is –40, –15, 10, 35,....

First term, a = –40 
Common difference, d = –15 – (–40) = 25

n^th term of the AP,

a_n = a + (n – 1)d 

= –40 + (n – 1) × 25

∴ 15^th term of the AP,

a₁₅ = –40 + (15 – 1) × 25 

= –40 + 350 

= 310