Given: Sum of n terms of an AP=n2−2n . To find: The fifth term = ? Sum of ' n ' terms of an AP=n2−2n ∴ Sum of 1st 5 terms ⇒S5=52−2⋅(5) =25−10=15 Similarly, Now, Sum of first 4 terms S4=42−2⋅(4) =16−8=8 ∴ The 5 th term of an AP ⇒T5=S5−S4...(UsingTn=Sn−Sn−1) =15−8 =7