Question

Calcule a soma dos 30 primeiros termos da P.A ( 1, 4...)

Answer 1

resolução!

r = a2 - a1

r = 4 - 1

r = 3

____________________________________________

a30 = a1 + 29r

a30 = 1 + 29 * 3

a30 = 1 + 87

a30 = 88

______________________________________________

Sn = ( a1 + an ) n / 2

Sn = ( 1 + 88 ) 30 / 2

Sn = 89 * 30 / 2

Sn = 2670 / 2

Sn = 1335

espero ter ajudado

Answer 2

$\large\boxed{\boxed{\boxed{{Ol\'a\:Dudinha}}}}}$

$\large\boxed{\boxed{{a_{n}=a_{1}+(n-1)r}}}}}$

Onde:

$a_{1}=1$

$n=30$

$r=a_{2}-a_{1}=4-1=3$

$a_{n}=a_{30}=???$

Logo:

$a_{30}=1+(30-1).3$

$a_{30}=1+29.3$

$a_{30}=1+87$

$a_{30}=88$

$\large\boxed{\boxed{{S_{n}=\frac{a_{1}+a_{n}}{2}.n}}}}}$

$S_{30}=\frac{1+88}{2}.30$

$S_{30}=\frac{89}{2}.30$

$S_{30}=44,5.30$

$\large\boxed{{S_{30}=1335}}}}}$

::::::::::Espero ter ajudado:::::::