Question

Calcule a soma dos 30 primeiros termos da PA (4, 9, 14, 19...)​

Answer 1

resolução!

r = a2 - a1

r = 9 - 4

r = 5

a30 = a1 + 29r

a30 = 4 + 29 * 5

a30 = 4 + 145

a30 = 149

Sn = ( a1 + an ) n / 2

Sn = ( 4 + 149 ) 30 / 2

Sn = 153 * 15

Sn = 2295

Answer 2

Resposta:

$\textsf{Segue a resposta abaixo}$

Explicação passo-a-passo:

$\mathsf{a_n=a_1+(n-1)\cdot r }$

$\mathsf{ a_{30}= 4+(30-1)\cdot5}$

$\mathsf{a_{30}=4+29\cdot5 }$

$\mathsf{a_{30}=4+145 }$

$\mathsf{ a_{30}=149}$

$\mathsf{ S_{n}=\dfrac{(a_1+a_n)\cdot n}{2}}$

$\mathsf{ S_{30}=\dfrac{(4+149)\cdot 30}{2}}$

$\mathsf{ S_{30}=\dfrac{153\cdot30}{2}}$

$\mathsf{S_{30}=\dfrac{4590}{2} }$

$\boxed{\boxed{ \mathsf{S_{30}=2295 }}}$