Let "a" be the middle term of the AP, and "d" be the common difference. Then you have these equations= , (1) and = . (2) Simplify (1) and (2): = (1') and = (2') Simplify (1'): = , which is the same as = , which is the same as = . (1'') Then (2') becomes (after substitution (1'') ) = , or = , or = = . Then a = = 2. Answer. The middle term under the question is 2.