If an arithmetic progression has a non-zero common difference, what is the nature of the sum \(S_n\) of its first \(n\) terms as a function of \(n\)?
Answer and explanation
Correct answer: Quadratic function
In \(S_n=\frac{n}{2}[2a+(n-1)d]\), the coefficient of \(n^2\) is \(\frac d2\). Since \(d\ne0\), \(S_n\) is quadratic, not linear. Exam tip: check the \(n^2\) term first.
Frequently asked questions
What is the correct answer to this question?
Quadratic function
Why is this the correct answer?
In \(S_n=\frac{n}{2}[2a+(n-1)d]\), the coefficient of \(n^2\) is \(\frac d2\). Since \(d\ne0\), \(S_n\) is quadratic, not linear. Exam tip: check the \(n^2\) term first.
Which subject and chapter does this question cover?
This is a Class 10 Mathematics question. Chapter: Arithmetic Progressions (AP). Topic: Finding the sum of the first $n$ terms of an AP.
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