数学课前练习

(2026·河南省·单元测试)已知数列\(\{a_n\}\)的前\(n\)项和\(S_n = kn^2 + 2n\)，\(a_5 = 11\)，则\(k\)的值为( )

A. 2

B. -2

C. 1

D. -1

(2025·江西省·月考试卷)若公差为\(d\)的等差数列\(\{a_n\}\)满足\(a_{n+1} + a_n = 4n - 3\)，则下列结论正确的有( )

A. 数列\(\{a_{n+1} + a_n\}\)也是等差数列

B. \(d = 2\)

C. \(a_1 = -\displaystyle \frac{1}{2}\)

D. 13是数列\(\{a_n\}\)中的项