Question

Va rog am nevoie urgent pana maine

Answer 1

Explicație pas cu pas:

7.

$a_{4} + a_{18} = a_{4} + a_{4} + (18 - 4) r = 2 \cdot a_{4} + 14r$

$a_{4} + a_{18} = 12 \implies 2 \cdot a_{4} + 14r = 12$

$a_{5} + a_{17} = a_{4} + r + a_{4} + (17 - 4) r = \\ = 2 \cdot a_{4} + r + 13r = 2 \cdot a_{4} + 14r = 12$