Solve r^2-4=-8

$$r ^ { 2 } - 4 = - 8$$

Solve for r

$$r=-2i$$

$$r=2i$$

Steps by Finding Square Root

Add 4 to both sides.

$$r^{2}=-8+4$$

Add -8 and 4 to get -4.

$$r^{2}=-4$$

The equation is now solved.

$$r=2i r=-2i$$

Steps Using the Quadratic Formula

Add 8 to both sides.

$$r^{2}-4+8=0$$

Add -4 and 8 to get 4.

$$r^{2}+4=0$$

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

$$r=\frac{0±\sqrt{0^{2}-4\times 4}}{2}$$

Square 0.

$$r=\frac{0±\sqrt{-4\times 4}}{2}$$

Multiply -4 times 4.

$$r=\frac{0±\sqrt{-16}}{2}$$

Take the square root of -16.

$$r=\frac{0±4i}{2}$$

Now solve the equation r=\frac{0±4i}{2} when ± is plus.

$$r=2i$$

Now solve the equation r=\frac{0±4i}{2} when ± is minus.

$$r=-2i$$

The equation is now solved.

$$r=2i r=-2i$$