$$x^{2}=10 \Rightarrow x=\pm \sqrt{10}$$

$$x^{2}=12 \Rightarrow x=\pm \sqrt{12}= \pm 2 \sqrt{3}$$

$$x^{2}=20 \Rightarrow x=\pm \sqrt{20}= \pm 2 \sqrt{5}$$

$$4x^{2}=9 \Rightarrow x^{2}=\frac{9}{4} \\ \Rightarrow x= \pm \sqrt{\frac{9}{4}}=\pm \frac{3}{2}$$

$$25x^{2}=16 \Rightarrow x^{2}=\frac{16}{25} \\ \Rightarrow x=\pm \sqrt{\frac{16}{25}}=\pm \frac{4}{5}$$

$$9x^{2}=2 \Rightarrow x^{2}=\frac{2}{9} \\ \Rightarrow x=\pm \sqrt{\frac{2}{9}}=\pm \frac{\sqrt{2}}{3}$$

$$4x^{2}=10\Rightarrow x^{2}=\frac{10}{4}\\ \Rightarrow x=\pm\sqrt{\frac{5}{2}}$$

$$4x^{2}=-9\Rightarrow x^{2}=\frac{-9}{4}$$

$$2x^{2}=9\Rightarrow x^{2}=\frac{9}{2}\Rightarrow x=\pm\sqrt{\frac{9}{2}}=\pm\frac{3}{\sqrt{2}}$$

$$\begin{array}{ll} x(x-10)=0 & \Rightarrow\left\{ \begin{array}{l} x=0\\ x-10=0 \end{array}\right.\\ & \Rightarrow\left\{ \begin{array}{l} x=0\\ x=10 \end{array}\right. \end{array}$$

$$\begin{array}{ll} 4x(x-2)=0 & \Rightarrow\left\{ \begin{array}{l} x=0\\ x-2=0 \end{array}\right.\\ & \Rightarrow\left\{ \begin{array}{l} x=0\\ x=2 \end{array}\right. \end{array}$$

$$\begin{array}{ll} x(2x-5)=0 & \Rightarrow\left\{ \begin{array}{l} x=0\\ 2x-5=0 \end{array}\right.\\ & \Rightarrow\left\{ \begin{array}{l} x=0\\ x=\frac{5}{2} \end{array}\right. \end{array}$$

$$x=\frac{7 \pm \sqrt{7^{2}-4(1)(6)}}{2(1)} = \\ =\frac{7\pm \sqrt{49-24}}{2} = \\ =\frac{7\pm\sqrt{25}}{2}= \\ = \frac{7\pm5}{2} =\left\{ \begin{array}{l} x=6\\ x=1 \end{array}\right.$$

$$x=\frac{5\pm \sqrt{5^{2}-4(4)(1)}}{2(4)} =\frac{5\pm \sqrt{25-16}}{8} = \\ \qquad =\frac{5\pm \sqrt{9}}{8}=\frac{5\pm3}{8}=\left{ \begin{array}{l}\frac{5+3}{8}=1\frac{5-3}{8}=\frac{1}{4}end{array} \right.$$

$$x=\frac{-2\pm \sqrt{2^{2}-4(2)(3)}}{2(1)} =\frac{-2\pm \sqrt{4-24}}{2} = \\ \qquad =\frac{-2\pm \sqrt{-20}}{2}$$
No tiene solución (en los reales)