To Find: 20^th term of the AP

Given: The series is √2, 3√2, 5√2, 7√2, ….

a₁=√2, a₂= 3√2 and d= 3√2–√2= 2√2

(Where a=a₁ is first term, a₂ is second term, a_n is nth term and d is common difference of given AP)

Formula Used: a_n = a + (n - 1)d

a₂₀= a₁ + (20 - 1)( 2√2)= √2 + 38√2= 39√2

So 20^rd term of AP is equal to 39√2.