- $ S = - \\\int_0^1 {f\\\left( x \\\right){\\\rm{d}}x} + \\\int_1^2 {f\\\left( x \\\right){\\\rm{d}}x}$ .
- $ S = \\\int_0^2 {f\\\left( x \\\right){\\\rm{d}}x}$ .
- $ S = \\\int_0^1 {f\\\left( x \\\right){\\\rm{d}}x} - \\\int_1^2 {f\\\left( x \\\right){\\\rm{d}}x}$ .
- $ S = \\\left| {\\\int_0^2 {f\\\left( x \\\right){\\\rm{d}}x} } \\\right|$.