Question

Find the 17th term of arithmetic progression whose 4th term is 5 and common difference is -2​

Answer 1

Answer:

Our basic formula is aₙ = a + (n-1) d

where a= first term, d= common difference, n= no. of terms, aₙ = value of given middle term

Here we have the value of the 4th term and have to find the 17th term, so we must use the 4th term as aₙ.

Substituting all provided values,

5 = a + (4-1) (-2)

⇒ 5 = a + (-6)

⇒ a = 11

Now, we have a so we can use the new number of terms as 17 and find out a₁₇.

Therefore, a₁₇ = 11 + (17-1)(-2)

⇒ a₁₇ = 11 +  (-32)

⇒ a₁₇ = -21