\[\boxed{\mathbf{22.}}\]
\[\textbf{а)}\ f(x) = 2x;\ \ x_{0} = 3;\ \mathrm{\Delta}x = 0,1:\ \]
\[\mathrm{\Delta}f = f\left( x_{0} + \mathrm{\Delta}x \right) - f\left( x_{0} \right) =\]
\[= f(3 + 0,1) - f(3) =\]
\[= 6,2 - 6 = 0,2.\]
\[\textbf{б)}\ f(x) = 2x;\ \ x_{0} = 4;\ \]
\[\mathrm{\Delta}x = - 0,1:\ \]
\[\mathrm{\Delta}f = f\left( x_{0} + \mathrm{\Delta}x \right) - f\left( x_{0} \right) =\]
\[= f(4 - 0,1) - f(4) =\]
\[= 7,8 - 8 = - 0,2.\]
\[\textbf{в)}\ f(x) = 2x;\ \ x_{0} = 0;\ \mathrm{\Delta}x = 0,1:\ \]
\[\mathrm{\Delta}f = f\left( x_{0} + \mathrm{\Delta}x \right) - f\left( x_{0} \right) =\]
\[= f(0 + 0,1) - f(0) =\]
\[= 0,2 - 0 = 0,2.\]
\[\textbf{г)}\ f(x) = 2x;\ \ x_{0} = 1;\ \mathrm{\Delta}x = 0,01:\ \]
\[\mathrm{\Delta}f = f\left( x_{0} + \mathrm{\Delta}x \right) - f\left( x_{0} \right) =\]
\[= f(1 + 0,01) - f(1) =\]
\[= 2,02 - 2 = 0,02.\]