Evaluate !! look at photo please i need help

Step-by-step explanation:

Given

See attachment

Required

Evaluate

The expression can be expressed as:

To do this, we  make use of sum of n terms of an AP.

When n = 1

--- T1

When n = 2

--- T2

When n - 26

--- T26

Next, we calculate d (common difference)

So, the sum is:

Let n = 26

So, we have:

Substitute values for T1 and T26