[tex]a_{1} = 10[/tex]
[tex]r = 5[/tex]
[tex]a_{100}=a_{1}+(n-1)r[/tex]
[tex]a_{100} = 10 + (100 - 1) \times 5[/tex]
[tex]a_{100} = 10 + 99 \times 5[/tex]
[tex]a_{100} = 10 + 495[/tex]
[tex]a_{100} = 505[/tex]
[tex]S_{100} = \frac{n(a_{1} + a_{100})}{2}[/tex]
[tex]S_{100} = \frac{100(10 + 505)}{2} [/tex]
[tex]S_{100} = \frac{100 \times 515}{2} = 50 \times 515 = 25750[/tex]
Formule :
[tex]a_{n}=a_{1}+(n-1)r[/tex]
[tex]S_{n} = \frac{n(a_{1} + a_{n})}{2}[/tex]
