\[\left( 7x^{2} - 4x + 8 \right) - \left( 4x^{2} + x - 5 \right) =\]
\[= 7x^{2} - 4x + 8 - 4x^{2} - x + 5 =\]
\[= 3x^{2} - 5x + 13\]