This type of quadratic equation (without the second term) can always be solved following the steps:
1 - Pass the linear coefficient to the other side.
2 - Divide by the quadratic coefficient (if there is one)
3 - Take the square root of each side (remeber the plus-minus sign)
Let's do it:
[tex]\begin{gathered} x^2+25=0 \\ x^2+25-25=0-25 \\ x^2=-25 \\ \sqrt[]{x^2}=\pm\sqrt[]{-25} \\ x=\pm i\sqrt[]{25} \\ x=\pm i\sqrt[]{5} \end{gathered}[/tex]
