IDNStudy.com, ang iyong mapagkukunan para sa malinaw at mabilis na mga sagot. Magtanong ng anumang bagay at makatanggap ng detalyadong sagot mula sa aming komunidad ng mga eksperto.

The second term of an arithmetic sequence is 24 and the fifth Is 3 find the first term and common difference. Showing the solution guys pls.

Sagot :

I am not sure if there is a shorter way in solving this one, but I can show you a solution only that it is a bit longer though.

Overview:
                       24                           3   

Formula:
             [tex] t_{n} = t_{1} + (n-1) d [/tex]
We will focus first in:   24                           3   
To find d:
Substitute:
               [tex] t_{n} [/tex] for 3
               [tex] t_{1} [/tex] for 24
                n for 4 
 3 = 24 + ( 4 -1 )d
 3 = 24 + 3d
 3 - 24 = 3d
 -21 = 3d
  - 21 / 3 = 3d /3
 -7 = d
We already have d = -7, we will go back to the original one.
             24                           3   

  [tex] t_{n} = t_{1} + (n-1) d [/tex]
Substitute:

3 = [tex] t_{1} [/tex] + (5 - 1) -7
3 = [tex] t_{1} [/tex] + -28
3 = [tex] t_{1} [/tex] - 28
3 + 28 = [tex] t_{1} [/tex]
31 = [tex] t_{1} [/tex]
                
So, the common difference (d) is -7, while the first term ([tex] t_{1} [/tex]) is 31
[tex]a_5-a_2=(5-2)d \\ 3-24=3d \\ -21=3d \\ -7=d[/tex]
We now have the common difference so:
[tex]a_n=a_1+(n-1)d \\ a_2=a_1+d \\ 24=a_1-7 \\ 31=a_1[/tex]