Question

Please help me thank you

Answer 1

418

Sn = ∑ 3 +4(n-1)

n=1

Explanation:

3,7,11,15,.....1671

a1 =3

d = 4 (7-3=4)

an = a1 + d(n-1)

an = 3 +4(n-1)

We need to determine the last term

1671 = 3 +4(n-1)

Subtract 3

1671-3 = 3-3 +4(n-1)

1668 = 4(n-1)

divide by 4

1668/4 = 4(n-1)/4

417 = n-1

Add 1 to each side

418 = n

418

Sn = ∑ a1 +d(n-1)

n=1

418

Sn = ∑ 3 +4(n-1)

n=1