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Use an explicit formula to find the 10th term of the geometric sequence. 2,8, 32, 128, ...

Use An Explicit Formula To Find The 10th Term Of The Geometric Sequence 28 32 128 class=

Sagot :

To find the explicit formula of a geometric sequence you use the next:

[tex]a_n=a_1\cdot r^{n-1}[/tex]

a1 is the first term in the sequence

r is the ratio between each pair of terms

2,8,32,128,...

Find r:

[tex]\begin{gathered} \frac{8}{2}=4 \\ \\ \frac{32}{8}=4 \\ \\ \frac{128}{32}=4 \end{gathered}[/tex]

Find the explicit formula:

[tex]a_n=2\cdot4^{n-1}[/tex]

To find the 10th term you substitute the n in the formula for 10:

[tex]\begin{gathered} a_{10}=2\cdot4^{10-1} \\ \\ a_{10}=2\cdot4^9_{}_{} \\ \\ a_{10}=2\cdot262144 \\ \\ a_{10}=524288 \end{gathered}[/tex]Then, the 10th term is 524,288