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#2: Given the geometric sequence 200, 100, 50, 25... (This one is tricky)
Write the explicit formula.
• Determine the 15th term of the sequence?

Sagot :

# 2: 200, 100, 50, 25 ... geometrik dizisi göz önüne alındığında (Bu biraz zor)
Açık formülü yazın.
• Dizinin 15. terimini belirleyin?

Answer:

see explanation

Step-by-step explanation:

The explicit formula for a geometric sequence is

[tex]a_{n}[/tex] = a₁ [tex](r)^{n-1}[/tex]

where a₁ is the first term and r the common ratio

Here a₁ = 200 and r = [tex]\frac{a_{2} }{a_{1} }[/tex] = [tex]\frac{100}{200}[/tex] = [tex]\frac{1}{2}[/tex] , then

[tex]a_{n}[/tex] = 200 [tex](\frac{1}{2}) ^{n-1}[/tex] ← explicit formula

The 15 th term is then

a₁₅ = 200 × [tex](\frac{1}{2}) ^{14}[/tex]

     = 200 × [tex]\frac{1}{16384}[/tex]

     = [tex]\frac{200}{16384}[/tex] ← divide numerator/ denominator by 8

     = [tex]\frac{25}{2048}[/tex]