If (a_n=7n^2+2n-5) then which statement is correct?
Answer and explanation
Correct answer: \(a_2=27\) and \(a_3=64\)
For the second term, substitute \(n=2\): \(a_2=7(2)^2+2(2)-5=28+4-5=27\). Similarly, for \(n=3\): \(a_3=7(3)^2+2(3)-5=63+6-5=64\). Hence, option A is correct. The other options result from an error in evaluating the \(n^2\) term or in addition/subtraction. Exam tip: substitute the value of \(n\) separately for each required term and check the arithmetic.
Frequently asked questions
What is the correct answer to this question?
\(a_2=27\) and \(a_3=64\)
Why is this the correct answer?
For the second term, substitute \(n=2\): \(a_2=7(2)^2+2(2)-5=28+4-5=27\). Similarly, for \(n=3\): \(a_3=7(3)^2+2(3)-5=63+6-5=64\). Hence, option A is correct. The other options result from an error in evaluating the \(n^2\) term or in addition/subtraction. Exam tip: substitute the value of \(n\) separately for each required term and check the arithmetic.
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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