x`_(t)=1
y`_(t)=2t
z`_(t)=3t^2
dl=sqrt(1^2+(2t)^2+(3t^2)^2)dt=[blue]sqrt(1+4t^2+9t^4)dt[/blue]
f(x;y;z)=sqrt(1+4y+9xz)=sqrt(1+4t^2+9t*t^3)=sqrt(1+4t^2+9t^4)
∫ _(L)sqrt(1+4y+9xz)dl= ∫ ^(1)_(0)sqrt(1+4t^2+9t^4)[blue]sqrt(1+4t^2+9t^4)dt[/blue]=
= ∫ ^(1)_(0)(1+4t^2+9t^4)dt=(t+(4t^3/3)+(9t^5/5))|^(1)_(0)=
=1+(4/3)+(9/5)=...