Hàm số \(f\left( x \right)\) xác định trên \(\mathbb{R}\backslash \left\{ 0 \right\}\) thỏa mãn \(f\left( x \right) = \frac{{{x^2} + 5x - 7}}{x}\).

a) Đ, b) Đ, c) Đ, d) S

a) \(f\left( x \right) = \frac{{{x^2} + 5x - 7}}{x} = x + 5 - \frac{7}{x}\).

b) \(\int {f\left( x \right)dx} = \frac{{{x^2}}}{2} + 5x - 7\ln \left| x \right| + C\).

c) Theo câu b, ta có \(F\left( x \right) = \frac{{{x^2}}}{2} + 5x - 7\ln \left| x \right| + C\) mà \(F\left( 1 \right) = 5\) nên \(\frac{{{1^2}}}{2} + 5.1 - 7\ln \left| 1 \right| + C = 5\)\( \Leftrightarrow C = \frac{1}{2}.\)

Do đó \(F\left( x \right) = \frac{{{x^2}}}{2} + 5x - 7\ln \left| x \right| + \frac{1}{2}\).

d) Theo câu b, ta có \(G\left( x \right) = \frac{{{x^2}}}{2} + 5x - 7\ln \left| x \right| + C\).

Suy ra \(G\left( x \right) = \left\{ \begin{array}{l}\frac{{{x^2}}}{2} + 5x - 7\ln x + {C_1}{\rm{ khi}}\;x \ge 0\\\frac{{{x^2}}}{2} + 5x - 7\ln \left( { - x} \right) + {C_2}{\rm{ khi}}\;x < 0\end{array} \right.\).

Vì \(G\left( 1 \right) = 4\) nên \(\frac{{{1^2}}}{2} + 5.1 - 7\ln 1 + {C_1} = 4 \Leftrightarrow {C_1} = - \frac{3}{2}\).

Suy ra \(G\left( 3 \right) = \frac{{{3^2}}}{2} + 5.3 - 7\ln 3 - \frac{3}{2} = 18 - 7\ln 3\). Suy ra \(G\left( { - 9} \right) = 2 + 7\ln 3\).

Do đó \(G\left( { - 9} \right) = \frac{{{{\left( { - 9} \right)}^2}}}{2} + 5.\left( { - 9} \right) - 7\ln 9 + {C_2} = 2 + 7\ln 3\)\( \Rightarrow {C_2} = \frac{{13}}{2} + 21\ln 3\).

Do đó \(G\left( { - 6} \right) = \frac{{{{\left( { - 6} \right)}^2}}}{2} + 5.\left( { - 6} \right) - 7\ln 6 + \frac{{13}}{2} + 21\ln 3\)\( = - 7\ln 2 + 14\ln 3 - \frac{{11}}{2}\).

Suy ra \(a = - 7;b = 14;c = - \frac{{11}}{2}\). Do đó \(a + b + c = \frac{3}{2}\).