[tex]4x^2+12x-7=0\\\\a=4;\ b=12;\ c=-7\\\Delta=b^2-4ac\\\\\Delta=12^2-4\cdot4\cdot(-7)=144+112=256 \ \textgreater \ 0\\\\therefore\\x_1=\dfrac{-b-\sqrt\Delta}{2a}\ and\ x_2=\dfrac{-b+\sqrt\Delta}{2a}\\\\\sqrt\Delta=\sqrt{256}=16\\\\x_1=\dfrac{-12-16}{2\cdot4}=\dfrac{-28}{8}=\boxed{-\dfrac{7}{2}}\\\\x_2=\dfrac{-12+16}{2\cdot4}=\dfrac{4}{8}=\boxed{\dfrac{1}{2}}[/tex]
