If (a_n=3n^2+5n-8), what is the value of (a_9-a_6)?
Answer and explanation
Correct answer: 150
Substituting the values in the given formula gives \(a_9=3(9)^2+5(9)-8=280\) and \(a_6=3(6)^2+5(6)-8=130\). Therefore, \(a_9-a_6=280-130=150\). Option 120 is incorrect because it uses 160 as the value of \(a_6\). Exam tip: Evaluate both terms separately before finding their difference.
Frequently asked questions
What is the correct answer to this question?
150
Why is this the correct answer?
Substituting the values in the given formula gives \(a_9=3(9)^2+5(9)-8=280\) and \(a_6=3(6)^2+5(6)-8=130\). Therefore, \(a_9-a_6=280-130=150\). Option 120 is incorrect because it uses 160 as the value of \(a_6\). Exam tip: Evaluate both terms separately before finding their difference.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
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