Question

Sa se determine progresia aritmetica ($a_{n}$) n$\geq$1 stiind ca:

$a_{1}$+$a_{2}$=8

$S_{4}$=22

Answer 1

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Answer 2

a1+a1+r=8⇒2a1+r=8⇒2a1=8-r
22=[(2a1+(n-1)r)*n]/2 
44=(8-r+3r)*4
11=8+2r
3=2r
r=3/2
a1=(8-r)/2⇒a1=(8-3/2)/2=13/4