Question

The 20^th term of the A.P.: `10sqrt(2), 6sqrt(2), 2sqrt(2),...` is:

पर्याय

• `-76 + 10sqrt(2)`

• `-62sqrt(2)`

• `-66sqrt(2)`

• `86sqrt(2)`

Answer 1

`bb(-66sqrt(2))`

Explanation:

A.P. = `10sqrt(2), 6sqrt(2), 2sqrt(2),...`

`a_1 = 10sqrt(2)` and `a_2 = 6sqrt(2)`

Common difference (d) = a₂ – a₁

= `6sqrt(2) - 10sqrt(2)`

= `-4sqrt(2)`

The 20^th term of A.P. (a₂₀)

= a + (n – 1) × d

= `10sqrt(2) + (20 - 1) xx (-4sqrt(2))`

= `10sqrt(2) + 19 xx (-4sqrt(2))`

= `10sqrt(2) - 76sqrt(2)`

= `-66sqrt(2)`