Amaya06amayaidn
Answered

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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 :

Jeremiaidn
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
Mlcparra16idn
[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]