Solve 2x^2+8=18

$$2 x ^ { 2 } + 8 = 18$$

Solve for x

$$x=\sqrt{5}\approx 2.236067977$$

$$x=-\sqrt{5}\approx -2.236067977$$

Steps by Finding Square Root

Subtract 8 from both sides.

$$2x^{2}=18-8$$

Subtract 8 from 18 to get 10.

$$2x^{2}=10$$

Divide both sides by 2.

$$x^{2}=\frac{10}{2}$$

Divide 10 by 2 to get 5.

$$x^{2}=5$$

Take the square root of both sides of the equation.

$$x=\sqrt{5} x=-\sqrt{5}$$

Steps Using the Quadratic Formula

Subtract 18 from both sides.

$$2x^{2}+8-18=0$$

Subtract 18 from 8 to get -10.

$$2x^{2}-10=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, 0 for b, and -10 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\times 2\left(-10\right)}}{2\times 2}$$

Square 0.

$$x=\frac{0±\sqrt{-4\times 2\left(-10\right)}}{2\times 2}$$

Multiply -4 times 2.

$$x=\frac{0±\sqrt{-8\left(-10\right)}}{2\times 2}$$

Multiply -8 times -10.

$$x=\frac{0±\sqrt{80}}{2\times 2}$$

Take the square root of 80.

$$x=\frac{0±4\sqrt{5}}{2\times 2}$$

Multiply 2 times 2.

$$x=\frac{0±4\sqrt{5}}{4}$$

Now solve the equation x=\frac{0±4\sqrt{5}}{4} when ± is plus.

$$x=\sqrt{5}$$

Now solve the equation x=\frac{0±4\sqrt{5}}{4} when ± is minus.

$$x=-\sqrt{5}$$

The equation is now solved.

$$x=\sqrt{5} x=-\sqrt{5}$$