Solve u^2+4=0

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

Solve for u

$$u=-2i$$

$$u=2i$$

Steps by Finding Square Root

Subtract 4 from both sides. Anything subtracted from zero gives its negation.

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

The equation is now solved.

$$u=2i u=-2i$$

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.

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

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}.

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

Square 0.

$$u=\frac{0±\sqrt{-4\times 4}}{2}$$

Multiply -4 times 4.

$$u=\frac{0±\sqrt{-16}}{2}$$

Take the square root of -16.

$$u=\frac{0±4i}{2}$$

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

$$u=2i$$

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

$$u=-2i$$

The equation is now solved.

$$u=2i u=-2i$$