Answer:
Step-by-step explanation:
a) [tex]t_{n}[/tex] = 2n - 3
[tex]t_{1}=2*1-3 = 2-3=-1\\\\t_{2}=2*2-3=4-3=1\\\\t_{3}=2*3-3=6-3=3\\\\t_{4}=2*4-3=8-3=5\\\\S_{4}=t_{1}+t_{2}+t_{3}+t_{4}\\\\= -1 + 1 + 3 + 5 \\\\= 8[/tex]
d)
[tex]t_{n}=\frac{2n-1}{2n+1}\\\\\\t_{1}=\frac{2-1}{2+1}=\frac{1}{3}\\\\t_{2}=\frac{4-1}{4+1}=\frac{3}{5}\\\\t_{3}=\frac{6-1}{6+1}=\frac{5}{7}\\\\t_{4}=\frac{8-1}{8+1}=\frac{7}{9}\\\\[/tex]
[tex]S_{n}=\frac{n}{2}(a+l)\\\\S_{4}=\frac{4}{2}(\frac{1}{3}+\frac{7}{9})\\\\=2*(\frac{1*3}{3*3}+\frac{7}{9})\\\\=2*(\frac{3}{9}+\frac{7}{9})\\\\=2*\frac{10}{9}\\\\=\frac{20}{9}[/tex]
