Question

calcule a soma dos 60 primeiros termos da p.a. (4,11,...)

Answer 1

$> resolucao \\ \\ \geqslant progressao \: aritmetica \\ \\ r = a2 - a1 \\ r = 11 - 4 \\ r = 7 \\ \\ > o \: 60 \: termo \: da \: pa \\ \\ an = a1 + (n - 1)r \\ an = 4 + (60 - 1)7 \\ an = 4 + 59 \times 7 \\ an = 4 + 413 \\ an = 417 \\ \\ \geqslant a \: soma \: dos \: 60 \: termos \: da \: pa \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(4 + 417)60}{2} \\ \\ sn = \frac{421 \times 60}{2} \\ \\ sn = 421 \times 30 \\ \\ sn = 12630 \\ \\ > < > < > < > < > < > < > >$