Geometric sequence equations. Game on.

Geometric sequence equations is a grade 9 math skill aligned to Common Core standard HSF.BF.A.2: write arithmetic and geometric sequences both recursively and with an explicit formula, and use them to model situations. Below are 8 practice questions with answers and step-by-step explanations, drawn from the 10 geometric sequence equations problems our math games drill.

CCSS HSF.BF.A.210 questions in the bank
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Warm-upeasy

The first term of a sequence is 22. Each term after the first is 44 times the preceding term. If ana_n represents the nnth term, which equation gives ana_n in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 2402 \cdot 4^{0}
2nd term, or
n=2:n = 2\textsf{:} 2412 \cdot 4^{1}
3rd term, or
n=3:n = 3\textsf{:} 2422 \cdot 4^{2}
4th term, or
n=4:n = 4\textsf{:} 2432 \cdot 4^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is an=24n1a_n = 2 \cdot 4^{n-1}.

Mid-gameeasy

The first term of a sequence is 88. Each term after the first is 22 times the preceding term. If f(n)f(n) represents the nnth term, which equation gives f(n)f(n) in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 8208 \cdot 2^{0}
2nd term, or
n=2:n = 2\textsf{:} 8218 \cdot 2^{1}
3rd term, or
n=3:n = 3\textsf{:} 8228 \cdot 2^{2}
4th term, or
n=4:n = 4\textsf{:} 8238 \cdot 2^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is f(n)=82n1f(n) = 8 \cdot 2^{n-1}.

Mid-gameeasy

The first term of a sequence is 66. Each term after the first is 33 times the preceding term. If ww represents the nnth term, which equation gives ww in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 6306 \cdot 3^{0}
2nd term, or
n=2:n = 2\textsf{:} 6316 \cdot 3^{1}
3rd term, or
n=3:n = 3\textsf{:} 6326 \cdot 3^{2}
4th term, or
n=4:n = 4\textsf{:} 6336 \cdot 3^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is w=63n1w = 6 \cdot 3^{n-1}.

Mid-gameeasy

The first term of a sequence is 1010. Each term after the first is 22 times the preceding term. If ana_n represents the nnth term, which equation gives ana_n in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 102010 \cdot 2^{0}
2nd term, or
n=2:n = 2\textsf{:} 102110 \cdot 2^{1}
3rd term, or
n=3:n = 3\textsf{:} 102210 \cdot 2^{2}
4th term, or
n=4:n = 4\textsf{:} 102310 \cdot 2^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is an=102n1a_n = 10 \cdot 2^{n-1}.

Mid-gameeasy

The first term of a sequence is 44. Each term after the first is 55 times the preceding term. If f(n)f(n) represents the nnth term, which equation gives f(n)f(n) in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 4504 \cdot 5^{0}
2nd term, or
n=2:n = 2\textsf{:} 4514 \cdot 5^{1}
3rd term, or
n=3:n = 3\textsf{:} 4524 \cdot 5^{2}
4th term, or
n=4:n = 4\textsf{:} 4534 \cdot 5^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is f(n)=45n1f(n) = 4 \cdot 5^{n-1}.

Mid-gameeasy

The first term of a sequence is 77. Each term after the first is 22 times the preceding term. If ww represents the nnth term, which equation gives ww in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 7207 \cdot 2^{0}
2nd term, or
n=2:n = 2\textsf{:} 7217 \cdot 2^{1}
3rd term, or
n=3:n = 3\textsf{:} 7227 \cdot 2^{2}
4th term, or
n=4:n = 4\textsf{:} 7237 \cdot 2^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is w=72n1w = 7 \cdot 2^{n-1}.

Mid-gameeasy

The first term of a sequence is 99. Each term after the first is 33 times the preceding term. If ana_n represents the nnth term, which equation gives ana_n in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 9309 \cdot 3^{0}
2nd term, or
n=2:n = 2\textsf{:} 9319 \cdot 3^{1}
3rd term, or
n=3:n = 3\textsf{:} 9329 \cdot 3^{2}
4th term, or
n=4:n = 4\textsf{:} 9339 \cdot 3^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is an=93n1a_n = 9 \cdot 3^{n-1}.

Buzzer beatermedium

The first term of a sequence is 33. Each term after the first is one-half the preceding term. If ww represents the nnth term, which equation gives ww in terms of nn?

Following the pattern:
1st term, or
n=1:n = 1\textsf{:} 3(12)03 \cdot \left(\dfrac{1}{2}\right)^{0}
2nd term, or
n=2:n = 2\textsf{:} 3(12)13 \cdot \left(\dfrac{1}{2}\right)^{1}
3rd term, or
n=3:n = 3\textsf{:} 3(12)23 \cdot \left(\dfrac{1}{2}\right)^{2}
4th term, or
n=4:n = 4\textsf{:} 3(12)33 \cdot \left(\dfrac{1}{2}\right)^{3}
Since each term has an exponent that is
11 less than the term number, the nnth term is w=3(12)n1w = 3 \cdot \left(\dfrac{1}{2}\right)^{n-1}.

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