Find the first term of a HP whpse secpmd ter, os `(5)/(4)` and the third term is `(1)/(2)`.

Explanation

Let a be the first term. Then, `a,(5)/(4),(1)/(2)` are in HP.
Then, `(a-(5)/(4))/((5)/(4)-(1)/(2))=(a)/((1)/(2)) " " [" from above note "]`
` implies (4a-5)/(5-2)=2a`
` implies 4a-5=6a " or " 2a=-5`
` therefore a=-(5)/(2)`