Use the quadratic formula, given by:
![x=\frac{-b\pm\sqrt[]{b^(2)-4ac}}{2a}](https://img.qammunity.org/2023/formulas/mathematics/college/7k7y3xb8tpc8g9j9690t1nd2zh42vpol1q.png)
where a, b and c are the coefficients of the equation:
ax² + bx + c = 0
By comparing the given equation 4x² + x - 9 = 0, with the previous general form, you have:
a = 4
b = 1
c = -9
replace the previous values of the parameters into the quadratic formula:
![\begin{gathered} x=\frac{-1\pm\sqrt[\square]{(1)^(2)-4(4)(-9)}}{2(4)} \\ x=\frac{-1\pm\sqrt[]{145}}{8} \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/lzdpvgn7j8l5fz6qq5a9symqalg2ax3z5g.png)
The previous expression contains the solutions to the given quadratic equation.