[tex]\displaystyle\bf\\\underbrace{(2x-7)(2x+7)}_{(2x)^{2}-7^{2}} =x(4x+3)\\\\4x^{2} -49=4x^{2} +3x\\\\4x^{2} -49-4x^{2} =3x\\\\3x=-49\\\\x=-16\frac{1}{3}[/tex]