If (a_n=4n^2-3n), what is the value of (a_5)?
Answer and explanation
Correct answer: 85
Given \(a_n=4n^2-3n\). To find the fifth term, substitute \(n=5\): \(a_5=4(5)^2-3(5)=4\times25-15=100-15=85\). Hence, the correct answer is 85. The value 100 comes from \(4\times5^2\) alone; the term \(-3n\) must also be subtracted. Exam tip: substitute the term number first, evaluate the power next, and then perform multiplication and subtraction.
Frequently asked questions
What is the correct answer to this question?
85
Why is this the correct answer?
Given \(a_n=4n^2-3n\). To find the fifth term, substitute \(n=5\): \(a_5=4(5)^2-3(5)=4\times25-15=100-15=85\). Hence, the correct answer is 85. The value 100 comes from \(4\times5^2\) alone; the term \(-3n\) must also be subtracted. Exam tip: substitute the term number first, evaluate the power next, and then perform multiplication and subtraction.
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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