Solve x*x=391

$$x \times x=391$$

Solve for x

$$x=\sqrt{391}\approx 19.773719933$$

$$x=-\sqrt{391}\approx -19.773719933$$

Steps by Finding Square Root

Multiply x and x to get x^{2}.

$$x^{2}=391$$

Take the square root of both sides of the equation.

$$x=\sqrt{391} x=-\sqrt{391}$$

Steps Using the Quadratic Formula

Multiply x and x to get x^{2}.

$$x^{2}=391$$

Subtract 391 from both sides.

$$x^{2}-391=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 0 for b, and -391 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\left(-391\right)}}{2}$$

Square 0.

$$x=\frac{0±\sqrt{-4\left(-391\right)}}{2}$$

Multiply -4 times -391.

$$x=\frac{0±\sqrt{1564}}{2}$$

Take the square root of 1564.

$$x=\frac{0±2\sqrt{391}}{2}$$

Now solve the equation x=\frac{0±2\sqrt{391}}{2} when ± is plus.

$$x=\sqrt{391}$$

Now solve the equation x=\frac{0±2\sqrt{391}}{2} when ± is minus.

$$x=-\sqrt{391}$$

The equation is now solved.

$$x=\sqrt{391} x=-\sqrt{391}$$