Answer :
Hello,
f(a+h)=3(a+h)+1=3a+3h+1
f(a)=3a+1
f(a+h)-f(a)=3a+3h+1-(3a+1)=3h
[tex] \lim_{h \to 0} \frac{f(a+h)-f(a)}{h}=\lim_{h \to 0}\frac{3h)}{h}=3[/tex]
f'(x)=3
f(a+h)=3(a+h)+1=3a+3h+1
f(a)=3a+1
f(a+h)-f(a)=3a+3h+1-(3a+1)=3h
[tex] \lim_{h \to 0} \frac{f(a+h)-f(a)}{h}=\lim_{h \to 0}\frac{3h)}{h}=3[/tex]
f'(x)=3