[tex](3x^{2}-x+1)+x^{2}(4-3x)=7\\\\ => 3x^{2}-x+1+4x^{2}-3x^{3}=7\\\\ => 4x^{2}-x-6=0\\\\ => 4.[x-2.\frac{1}{8}+(\frac{1}{8})^{2}]^{2}-4.(\frac{1}{8})^{2}-6=0\\\\ => 4.(x-\frac{1}{8})^{2}-4.\frac{1}{64}-6=0\\\\ => 4.(x-\frac{1}{8})^{2}-\frac{1}{16}-\frac{96}{16}=0\\\\ => 4.(x-\frac{1}{8})^{2}=\frac{97}{16}\\\\ =>....[/tex]