9514 1404 393
Answer:
5) 729, an=3^n, a[1]=3; a[n]=3·a[n-1]
6) 1792, an=7(4^(n-1)), a[1]=7; a[n]=4·a[n-1]
Step-by-step explanation:
The next term of a geometric sequence is the last term multiplied by the common ratio. (This is the basis of the recursive formula.)
The Explicit Rule is ...

for first term a₁ and common ratio r.
The Recursive Rule is ...
a[1] = a₁
a[n] = r·a[n-1]
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5. First term is a₁ = 3; common ratio is r = 9/3 = 3.
Next term: 243×3 = 729
Explicit rule: an = 3·3^(n-1) = 3^n
Recursive rule: a[1] = 3; a[n] = 3·a[n-1]
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6. First term is a₁ = 7; common ratio is r = 28/7 = 4.
Next term: 448×4 = 1792
Explicit rule: an = 7·4^(n-1)
Recursive rule: a[1] = 7; a[n] = 4·a[n-1]
Correct answers are:
(1) <span>28, 141 known cases
(2) 79913.71 known cases after six weeks (round off according to the options given)
(3) After approx. 9 weeks (9.0142 in decimal)
Explanations:
(1) Put x = 0 in given equation
</span><span>y= 28, 141 (1.19)^x
</span><span>y= 28, 141 (1.19)^(0)
</span>y= 28, 141
(2) Put x = 6 in the given equation:
<span>y= 28, 141 (1.19)^x
</span><span>y= 28, 141 (1.19)^(6)
</span>y= 79913.71
(3) Since
y= 28, 141 (1.19)^x
And y = <span>135,000
</span>135,000 = 28, 141 (1.19)^x
135,000/28, 141 = (1.19)^x
taking "ln" on both sides:
ln(4.797) = ln(1.19)^x
ln(4.797) = xln(1.19)
x = 9.0142 (in weeks)