5. Recursion and Iteration
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-9, -10, -12, -16, -24
a_1&=-9 a_(n+1)&=2a_n+8 To do so, we will use a table. To find a_2 we will substitute 1 for n in the above formula. To find a_3 we will substitute 2 for n, and so on.
| n | a_(n+1)=2a_n+8 | 2a_n+8 | a_(n+1) |
|---|---|---|---|
| - | a_1= -9 | - | - |
| 1 | a_(1+1)=2a_1+8 ⇕ a_2=2a_1+8 |
a_2=2 a_1+8 ⇓ a_2=2( -9)+8 |
a_2= -10 |
| 2 | a_(2+1)=2a_2+8 ⇕ a_3=2a_2+8 |
a_3=2 a_2+8 ⇓ a_3=2( -10)+8 |
a_3= -12 |
| 3 | a_(3+1)=2a_3+8 ⇕ a_4=2a_3+8 |
a_4=2 a_3+8 ⇓ a_4=2( -12)+8 |
a_4= -16 |
| 4 | a_(4+1)=2a_4+8 ⇕ a_5=2a_4+8 |
a_5=2 a_4+8 ⇓ a_5=2( -16)+8 |
a_5= -24 |
The first five terms of the sequence are -9, -10, -12, -16, and -24.