Answer
$$h'\left( x \right) = - 12.8{\left( {6.4x - 3} \right)^{ - 3}} - 8.6{\left( {4.3x - 1} \right)^{ - 3}}$$
Work Step by Step
$$\eqalign{
& f\left( x \right) = {\left( {6.4x - 3} \right)^{ - 2}} + {\left( {4.3x - 1} \right)^{ - 2}} \cr
& {\text{Differentiate}} \cr
& h'\left( x \right) = \frac{d}{{dx}}\left( {{{\left( {6.4x - 3} \right)}^{ - 2}}} \right) + \frac{d}{{dx}}\left( {{{\left( {4.3x - 1} \right)}^{ - 2}}} \right) \cr
& {\text{Use the chain rule and the power rule }}\frac{d}{{dx}}\left[ {{u^n}} \right] = n{u^{n - 1}}u' \cr
& h'\left( x \right) = - 2{\left( {6.4x - 3} \right)^{ - 3}}\left( {6.4} \right) - 2{\left( {4.3x - 1} \right)^{ - 3}}\left( {4.3} \right) \cr
& {\text{Simplifying}} \cr
& h'\left( x \right) = - 12.8{\left( {6.4x - 3} \right)^{ - 3}} - 8.6{\left( {4.3x - 1} \right)^{ - 3}} \cr} $$