4-7х^      6х^2 ------ -  ------- 2-х        2-х             3 при х= - --             4

[latex]\frac{4-7x^2}{2-x}-\frac{6x^2}{2-x}=\frac{4-7x^2-6x^2}{2-x}=\frac{4-13x^2}{2-x}[/latex]   [latex]\frac{4-13x^2}{2-x}=\frac{4-13\cdot(\frac{3}{4})^2}{2-\frac{3}{4}}=\frac{4-13\cdot\frac{9}{16}}{\frac{5}{4}}=\frac{4(4-\frac{117}{16})}{5}=\frac{16-\frac{117}{4}}{5}=\frac{-\frac{53}{4}}{5}==-\frac{53}{5\cdot4}=-\frac{53}{20}=-2,65[/latex]