Question

calcule a soma dos 40 primerios termos da p.a (12,16)

Answer 1

$r=16-12=4$

$a_{40}=a_{2}+38r\\a_{40}=16+38.4=168$

$s_{40}=\dfrac{\cancel{40}(168+12)}{\cancel{2}}$

$\boxed{\boxed{\mathsf{s_{40}=20.180=3600}}}$