Q. Find the 9th term of the geometric sequence 1,−4,16,…Answer:
Identify Common Ratio: To find the 9th term of a geometric sequence, we need to identify the common ratio (r) of the sequence. The common ratio is found by dividing any term by the previous term.Calculation: r=(−4)/1=−4
Use Formula for nth Term: Now that we have the common ratio, we can use the formula for the nth term of a geometric sequence, which is an=a1×r(n−1), where a1 is the first term and n is the term number.
Calculate for 9th Term: We are looking for the 9th term n=9, and we know the first term a1 is 1, and the common ratio r is −4.Calculation: a9=1×(−4)9−1=1×(−4)8
Calculate (−4)8: Now we calculate (−4)8. Since −4 is raised to an even power, the result will be positive.Calculation: (−4)8=65536
Multiply First Term: Finally, we multiply the first term by the result of (−4)8 to find the 9th term.Calculation: a9=1×65536=65536