a)
f(x)=√2x +1
f(1)=√2×1 +1=√2 +1
f(-1)=√2×(-1) +1=-√2 +1
ma=(√2 +1-√2 +1)/2=2/2=1
b)
f(√2)=√2×√2 +1=2 +1=3
f(13√2)=√2×13√2 +1=13×2 +1=27
mg=√3×27=√81=9
c)
f(a)=√2×a +1=√2a+1
f(b)=√2×b +1=√2b+1
A=√2×(√2a+1-√2b-1)=2(a-b) ∈Z