If \(a_n=3\cdot2^n+2n^2\), what is the value of \(a_4\)?
Answer and explanation
Correct answer: 80
Substituting \(n=4\), \(a_4=3\cdot2^4+2(4)^2=3\cdot16+2\cdot16=48+32=80\). Therefore, 80 is correct. An answer such as 76 can result from incorrectly evaluating either the exponential or squared term. Exam tip: calculate \(2^4\) and \(4^2\) separately before multiplying by their coefficients.
Frequently asked questions
What is the correct answer to this question?
80
Why is this the correct answer?
Substituting \(n=4\), \(a_4=3\cdot2^4+2(4)^2=3\cdot16+2\cdot16=48+32=80\). Therefore, 80 is correct. An answer such as 76 can result from incorrectly evaluating either the exponential or squared term. Exam tip: calculate \(2^4\) and \(4^2\) separately before multiplying by their coefficients.
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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