Cho tổng \(S_n=1+3+6+\cdots+\dfrac{n(n+1)}{2}\), với \(n\) là số nguyên dương tùy ý. Tìm \(S_{k+1}\).

	\(S_{k+1}=1+3+6+\cdots+\dfrac{k(k+1)}{2}+\dfrac{(k+1)(k+2)}{2}\)
	\(S_{k+1}=1+3+6+\cdots+\dfrac{(k-1)k}{2}+\dfrac{k(k+1)}{2}\)
	\(S_{k+1}=\dfrac{(k+1)(k+2)}{2}\)
	\(S_{k+1}=\dfrac{k(k+1)}{2}\)