Resposta :
[tex]a_{n} = a_{1} + (n - 1)r[/tex]
[tex]a_{4} = a_{1} + (4 - 1)r[/tex]
[tex]a_{4} = a_{1} + 3r[/tex]
[tex]25 = a_{1} + 3(-5)[/tex]
[tex]25=a_{1}-15[/tex]
[tex]25+15=a_{1}[/tex]
[tex]40=a_{1}[/tex]
[tex]a_{n} = a_{1} + (n - 1)r[/tex]
[tex]a_{7} = a_{1} + (7 - 1)r[/tex]
[tex]a_{7} = a_{1} + 6r[/tex]
[tex]a_{7} = 40 + 6(-5)[/tex]
[tex]a_{7} = 40 - 30[/tex]
[tex]a_{7} = 10[/tex]
[tex]a_{4} = a_{1} + (4 - 1)r[/tex]
[tex]a_{4} = a_{1} + 3r[/tex]
[tex]25 = a_{1} + 3(-5)[/tex]
[tex]25=a_{1}-15[/tex]
[tex]25+15=a_{1}[/tex]
[tex]40=a_{1}[/tex]
[tex]a_{n} = a_{1} + (n - 1)r[/tex]
[tex]a_{7} = a_{1} + (7 - 1)r[/tex]
[tex]a_{7} = a_{1} + 6r[/tex]
[tex]a_{7} = 40 + 6(-5)[/tex]
[tex]a_{7} = 40 - 30[/tex]
[tex]a_{7} = 10[/tex]