Question

calcule a soma dos numeros positivos 2,4,6, 8...98

Answer 1

a1 = 2
a2 = 4
r = 4 - 2 = 2 ***
an = 98
98 = a1 + (n-1)r
98 = 2 + ( n - 1)2
98 = 2 + 2n - 2
2n = 98
n = 49 ****
S49 = ( 2 + 98)*49/2
S49 = 100 * 49/2 = 4900/2 = 2450 ***