Answer:
f(5) = 21
Step-by-step explanation:
Given:
[tex]f(0)=1[/tex]
[tex]f(n)=f(n-1)+n+1[/tex]
[tex]\implies f(1)=f(0)+1+1=1 + 1 + 1=3[/tex]
[tex]\implies f(2)=f(1)+2+1=3 + 2 + 1=6[/tex]
[tex]\implies f(3)=f(2)+3+1=6+3+1=10[/tex]
[tex]\implies f(4)=f(3)+4+1=10+4+1=15[/tex]
[tex]\implies f(5)=f(4)+5+1=15+5+1=21[/tex]
