Question

HELP MEEE!DAU COROANĂ!
Problema 5!

Answer 1

$a_{7}=a_{1}+(7-1)*r=a_{1}+6*r\\a_{3}=a_{1}+(3-1)*r=a_{1}+2*r\\ \\a_{7}=a_{3}+4 =>a_{1}+6*r=a_{1}+2*r+4$

Scădem $a_{1}$ :

$6*r=2*r+4//-2*r\\4*r=4//:4\\r=1$