4.
[tex]a_1=-20,\ a_3=-15\\\\2d=a_3-a_1\to 2d=-15-(-20)\to2d=-15+20\to2d=5\to d=2.5\\\\a_n=a_1+(n-1)d\to a_n=-20+(n-1)(2.5)=-20+2.5n-2.5=2.5n-22.5\\\\a_2=2.5(2)-22.5=5-22.5=-17.5\\\\a_4=2.5(4)-22.5=10-22.5=-12.5\\\\a_6=2.5(6)-22.5=15-22.5=-7.5[/tex]
n | 1 | 2 | 3 | 4 | 5 | 6 |
f(n)| -20 | -17.5 | -15 |-12.5| -10 | -7.5 |
First term: -20 Common Difference: 2.5
Explicit Rule: [tex]a_n=2.5n-22.5[/tex] Recursive Rule: [tex]a_1=-20,\ a_n=a_{n-1}+2.5[/tex]
5.
[tex]a_1=123,\ a_2=131\\\\d=a_2-a_1\to d=131-123=8\\\\a_n=a_1+(n-1)d\to a_n=123+(n-1)(8)=123+8n-8=8n+115\\\\a_3=8(3)+115=24+115=139\\\\a_5=8(5)+115=40+115=155\\\\a_6=8(6)+115=48+115=163[/tex]
n | 1 | 2 | 3 | 4 | 5 | 6 |
f(n)| 123 | 131 | 139 | 147 | 155 | 163 |
First term: 123 Common Difference: 8
Explicit Rule: [tex]a_n=8n+115[/tex] Recursive Rule: [tex]a_1=20,\ a_n=a_{n-1}+8[/tex]
