If \(a_n=\frac{3n^2+5n}{4}\), what is the value of \(a_4\)?
Answer and explanation
Correct answer: 17
Substitute \(n=4\): \(a_4=\frac{3(4)^2+5(4)}{4}=\frac{3\times16+20}{4}=\frac{68}{4}=17\). Therefore, 17 is correct. Getting 16 may result from incorrectly evaluating \(3\times4^2\) or making an error in the numerator. Exam tip: substitute the value of \(n\) first, evaluate the power, and then simplify the numerator and denominator.
Frequently asked questions
What is the correct answer to this question?
17
Why is this the correct answer?
Substitute \(n=4\): \(a_4=\frac{3(4)^2+5(4)}{4}=\frac{3\times16+20}{4}=\frac{68}{4}=17\). Therefore, 17 is correct. Getting 16 may result from incorrectly evaluating \(3\times4^2\) or making an error in the numerator. Exam tip: substitute the value of \(n\) first, evaluate the power, and then simplify the numerator and denominator.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
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