=
2
a
1
+a
n
\large \text {$a_{1} = 2 $}a
1
=2
\large \text {$a_{2} = 4 $}a
2
=4
\large \text {$a_{n} = a_{7} = 14 $}a
n
=a
7
=14
\large \text {$n = 7 $}n=7
a) Razão
\large \text {$r = a_{2} - a_{1} $}r=a
2
−a
1
\large \text {$r = 4 - 2 $}r=4−2
\large \text {$\boxed{r = 2} $}
r=2
\Large \text {$a_{m} =\frac{a_{1}+ a_{n} }{2} $}a
m
=
2
a
1
+a
n
\Large \text {$a_{m} =\frac{2 + 14 }{2} $}a
m
=
2
2+14
\Large \text {$a_{m} =\frac{16 }{2} $}a
m
=
2
16
\Large \text {$ \boxed{a_{m} =8} $}
a
m
=8
\large \text {$S_{n} = \frac{n.(a_{1} + a_{n})}{2} $}S
n
=
2
n.(a
1
+a
n
)
\large \text {$S_{7} = \frac{7.(2 + 14)}{2} $}S
7
=
2
7.(2+14)
\large \text {$S_{7} = \frac{7.16}{2} $}S
7
=
2
7.16
\large \text {$S_{7} = \frac{112}{2} $}S
7
=
2
112
\large \text {$ \boxed{S_{7} = 56} $}
S
7
=56
