5.
已知数列\(\{a_{n}\}\),\(\{b_{n}\}\)均为各项都不相等的数列,\(S_{n}\)为\(\{a_{n}\}\)的前\(n\)项和,\(a_{n+1}b_{n}=S_{n}+1(n∈N^{*}).\)
\((1)\) 若\(a_{1}=1\),\(b_{n}=\dfrac{n}{2}\),求\(a_{4}\)的值\(;\)
\((2)\) 若\(\{a_{n}\}\)是公比为\(q\)的等比数列,求证:存在实数\(λ\),使得\(\{b_{n}+λ\}\)为等比数列\(;\)
\((3)\) 若\(\{a_{n}\}\)的各项都不为零,\(\{b_{n}\}\)是公差为\(d\)的等差数列,求证:\(a_{2}\),\(a_{3}\),\(…\),\(a_{n}\),\(…\)成等差数列的充要条件是\(d=\dfrac{1}{2}\).