Question

which term of arithmetic progression
2,-1,-4,-7 is -40​

Answer 1

Answer:

15th term is -40

Step-by-step explanation:

$a = 2 \\ d = - 1 - (2) = - 3 \\ T_{n} = - 40 \\ \\ T_{n} = a + (n - 1)d \\ - 40 = 2 + (n - 1) - 3 \\ - 40 = 2 + ( - 3n) + 3 \\ - 40 = 2 - 3n + 3 \\ - 40 = 5 - 3n \\ 3n = 5 + 40 \\ 3n = 45 \\ n = \frac{45}{3} \\ \boxed{ \large n = \underline{ \underline{ 15}}}$