First 100 terms of the following sequence 3 ,7 ,11

Given that [tex]a_1 = 3, d = 4[/tex]

Find the nth term:

[tex]a_n = 3 + 4(n - 1)[/tex]

[tex]a_n = 3 + 4n - 4[/tex]

[tex]a_n = 4n - 1[/tex]

Find the 100th term:

[tex]a_{100} = 4(100) - 1 = 399[/tex]

Find the Sum:

[tex]\text{Sum} = 100(\dfrac{a_1 + a_{100}}{2} )= 100 (\dfrac{3 + 399}{2}) = 20100[/tex]