Solve 5x^2-720=0

$$5 x ^ { 2 } - 720 = 0$$

Solve for x

$$x=12$$

$$x=-12$$

Steps Using Difference of Squares

Divide both sides by 5.

$$x^{2}-144=0$$

Consider x^{2}-144. Rewrite x^{2}-144 as x^{2}-12^{2}. The difference of squares can be factored using the rule: a^{2}-b^{2}=\left(a-b\right)\left(a+b\right).

$$\left(x-12\right)\left(x+12\right)=0$$

To find equation solutions, solve x-12=0 and x+12=0.

$$x=12 x=-12$$

Steps by Finding Square Root

Add 720 to both sides. Anything plus zero gives itself.

$$5x^{2}=720$$

Divide both sides by 5.

$$x^{2}=\frac{720}{5}$$

Divide 720 by 5 to get 144.

$$x^{2}=144$$

Take the square root of both sides of the equation.

$$x=12 x=-12$$

Steps Using the Quadratic Formula

Quadratic equations like this one, with an x^{2} term but no x term, can still be solved using the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}, once they are put in standard form: ax^{2}+bx+c=0.

$$5x^{2}-720=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 5 for a, 0 for b, and -720 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\times 5\left(-720\right)}}{2\times 5}$$

Square 0.

$$x=\frac{0±\sqrt{-4\times 5\left(-720\right)}}{2\times 5}$$

Multiply -4 times 5.

$$x=\frac{0±\sqrt{-20\left(-720\right)}}{2\times 5}$$

Multiply -20 times -720.

$$x=\frac{0±\sqrt{14400}}{2\times 5}$$

Take the square root of 14400.

$$x=\frac{0±120}{2\times 5}$$

Multiply 2 times 5.

$$x=\frac{0±120}{10}$$

Now solve the equation x=\frac{0±120}{10} when ± is plus. Divide 120 by 10.

$$x=12$$

Now solve the equation x=\frac{0±120}{10} when ± is minus. Divide -120 by 10.

$$x=-12$$

The equation is now solved.

$$x=12 x=-12$$