Solve -2x^2+36+6=0

$$- 2 x ^ { 2 } + 36 + 6 = 0$$

Solve for x

$$x=\sqrt{21}\approx 4.582575695$$

$$x=-\sqrt{21}\approx -4.582575695$$

Steps by Finding Square Root

Add 36 and 6 to get 42.

$$-2x^{2}+42=0$$

Subtract 42 from both sides. Anything subtracted from zero gives its negation.

$$-2x^{2}=-42$$

Divide both sides by -2.

$$x^{2}=\frac{-42}{-2}$$

Divide -42 by -2 to get 21.

$$x^{2}=21$$

Take the square root of both sides of the equation.

$$x=\sqrt{21} x=-\sqrt{21}$$

Steps Using the Quadratic Formula

Add 36 and 6 to get 42.

$$-2x^{2}+42=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute -2 for a, 0 for b, and 42 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\left(-2\right)\times 42}}{2\left(-2\right)}$$

Square 0.

$$x=\frac{0±\sqrt{-4\left(-2\right)\times 42}}{2\left(-2\right)}$$

Multiply -4 times -2.

$$x=\frac{0±\sqrt{8\times 42}}{2\left(-2\right)}$$

Multiply 8 times 42.

$$x=\frac{0±\sqrt{336}}{2\left(-2\right)}$$

Take the square root of 336.

$$x=\frac{0±4\sqrt{21}}{2\left(-2\right)}$$

Multiply 2 times -2.

$$x=\frac{0±4\sqrt{21}}{-4}$$

Now solve the equation x=\frac{0±4\sqrt{21}}{-4} when ± is plus.

$$x=-\sqrt{21}$$

Now solve the equation x=\frac{0±4\sqrt{21}}{-4} when ± is minus.

$$x=\sqrt{21}$$

The equation is now solved.

$$x=-\sqrt{21} x=\sqrt{21}$$