Solve k^2=8k

$$k ^ { 2 } = 8 k$$

Solve for k

$$k=8$$

$$k=0$$

Steps Using Factoring

Subtract 8k from both sides.

$$k^{2}-8k=0$$

Factor out k.

$$k\left(k-8\right)=0$$

To find equation solutions, solve k=0 and k-8=0.

$$k=0 k=8$$

Steps Using the Quadratic Formula

Subtract 8k from both sides.

$$k^{2}-8k=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, -8 for b, and 0 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$k=\frac{-\left(-8\right)±\sqrt{\left(-8\right)^{2}}}{2}$$

Take the square root of \left(-8\right)^{2}.

$$k=\frac{-\left(-8\right)±8}{2}$$

The opposite of -8 is 8.

$$k=\frac{8±8}{2}$$

Now solve the equation k=\frac{8±8}{2} when ± is plus. Add 8 to 8.

$$k=\frac{16}{2}$$

Divide 16 by 2.

$$k=8$$

Now solve the equation k=\frac{8±8}{2} when ± is minus. Subtract 8 from 8.

$$k=\frac{0}{2}$$

Divide 0 by 2.

$$k=0$$

The equation is now solved.

$$k=8 k=0$$

Steps for Completing the Square

Subtract 8k from both sides.

$$k^{2}-8k=0$$

Divide -8, the coefficient of the x term, by 2 to get -4. Then add the square of -4 to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$k^{2}-8k+\left(-4\right)^{2}=\left(-4\right)^{2}$$

Square -4.

$$k^{2}-8k+16=16$$

Factor k^{2}-8k+16. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(k-4\right)^{2}=16$$

Take the square root of both sides of the equation.

$$\sqrt{\left(k-4\right)^{2}}=\sqrt{16}$$

Simplify.

$$k-4=4 k-4=-4$$

Add 4 to both sides of the equation.

$$k=8 k=0$$