If (a_n=3^n-2), what is (a_4)?
Answer and explanation
Correct answer: 79
Given (a_n=3^n-2), substitute n=4: (a_4=3^4-2=81-2=79). Therefore, 79 is correct. The closest distractor, 81, is only the value of (3^4); 2 must still be subtracted. Exam tip: for an nth-term formula, substitute the given value of n first, evaluate powers, and then perform the remaining operations.
Frequently asked questions
What is the correct answer to this question?
79
Why is this the correct answer?
Given (a_n=3^n-2), substitute n=4: (a_4=3^4-2=81-2=79). Therefore, 79 is correct. The closest distractor, 81, is only the value of (3^4); 2 must still be subtracted. Exam tip: for an nth-term formula, substitute the given value of n first, evaluate powers, and then perform the remaining operations.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
