Resposta:
74.250
Explicação passo-a-passo:
[tex]sn = \frac{(a1 + a n) \times n\: }{2} [/tex]
a1=505
an=995
r=5
n=?
an=a1+(n-1)•r
995=505+(n-1)•5
995-505=5n-5
995-505+5=5n
490+5=5n
495=5n
n=495/5
n=99
[tex]sn = \frac{(505 + 995) \times 99}{2} [/tex]
[tex]sn = \ \frac{(1500) \times 99}{2} [/tex]
[tex]sn = \frac{148.500}{2} [/tex]
[tex]sn = 74.250[/tex]
