razão = 6 - 10

razão = -4

achando a100

a100 = a1 + 99r

a100 = 10 + 99*(-4)

a100 = 10 - 396

a100 = -386

S100 = (a1 + a100). 100/2

S100 = ( 10 - 386) . 100/2

S100 = -376 . 100/2

S100 = -18.800

atte Colossoblack

[tex] > resolucao \\ \\ \geqslant progressao \: aritmetica \\ \\ r = 2 - a1 \\ r = 6 - 10 \\ r = - 4 \\ \\ \\ an = a1 + (n - 1)r \\ an = 10 + (101 - 1) - 4 \\ an = 10 + 100 \times ( - 4) \\ an = 10 + ( - 400) \\ an = 10 - 400 \\ an = - 390 \\ \\ \\ \\ \geqslant soma \: dos \: termos \: da \: pa \: \\ \\ sn = \frac{(a1 + an)n}{2} \\ \\ sn = \frac{(10 + ( - 390)101}{2} \\ \\ sn = \frac{ - 380 \times 101}{2} \\ \\ sn = - 190 \times 101 \\ \\ sn = - 19190 \\ \\ \\ \\ > < > < > < > < > < > < > [/tex]