Q. Find the 9th term of the geometric sequence shown below.−4x6,4x11,−4x16,…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.
Calculate common ratio: Let's find the common ratio by dividing the second term by the first term: r=−4x64x11=−x5
Find 9th term formula: Now that we have the common ratio, we can find the 9th term a9 using the formula for the nth term of a geometric sequence: an=a1⋅r(n−1), where a1 is the first term and n is the term number.
Substitute values in formula: The first term a1 is −4x6. We want to find the 9th term a9, so we plug in the values into the formula:a9=(−4x6)⋅(−x5)9−1
Simplify exponent: Simplify the exponent in the formula: a9=(−4x6)⋅(−x5)8
Calculate power: Now, we calculate the power of −x5 raised to the 8th power:(−x5)8=x5∗8=x40Since the base is negative and the exponent is even, the result will be positive.
Multiply terms: Multiply the first term by the result we just found: a9=(−4x6)×x40
Combine like terms: Combine the like terms by adding the exponents: a9=−4x(6+40)=−4x46
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