Solve (x-2)(x+2)=16

$$(x-2)(x+2)=16$$

Solve for x

$$x=2\sqrt{5}\approx 4.472135955$$

$$x=-2\sqrt{5}\approx -4.472135955$$

Steps by Finding Square Root

Consider \left(x-2\right)\left(x+2\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 2.

$$x^{2}-4=16$$

Add 4 to both sides.

$$x^{2}=16+4$$

Add 16 and 4 to get 20.

$$x^{2}=20$$

Take the square root of both sides of the equation.

$$x=2\sqrt{5} x=-2\sqrt{5}$$

Steps Using the Quadratic Formula

Consider \left(x-2\right)\left(x+2\right). Multiplication can be transformed into difference of squares using the rule: \left(a-b\right)\left(a+b\right)=a^{2}-b^{2}. Square 2.

$$x^{2}-4=16$$

Subtract 16 from both sides.

$$x^{2}-4-16=0$$

Subtract 16 from -4 to get -20.

$$x^{2}-20=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 0 for b, and -20 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{0±\sqrt{0^{2}-4\left(-20\right)}}{2}$$

Square 0.

$$x=\frac{0±\sqrt{-4\left(-20\right)}}{2}$$

Multiply -4 times -20.

$$x=\frac{0±\sqrt{80}}{2}$$

Take the square root of 80.

$$x=\frac{0±4\sqrt{5}}{2}$$

Now solve the equation x=\frac{0±4\sqrt{5}}{2} when ± is plus.

$$x=2\sqrt{5}$$

Now solve the equation x=\frac{0±4\sqrt{5}}{2} when ± is minus.

$$x=-2\sqrt{5}$$

The equation is now solved.

$$x=2\sqrt{5} x=-2\sqrt{5}$$