Solve -x^2+18x

$$- x ^ { 2 } + 18 x$$

Factor

$$x\left(18-x\right)$$

Solution Steps

Factor out x.

$$x\left(-x+18\right)$$

Steps Using the Quadratic Formula

Quadratic polynomial can be factored using the transformation ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right), where x_{1} and x_{2} are the solutions of the quadratic equation ax^{2}+bx+c=0.

$$-x^{2}+18x=0$$

All equations of the form ax^{2}+bx+c=0 can be solved using the quadratic formula: \frac{-b±\sqrt{b^{2}-4ac}}{2a}. The quadratic formula gives two solutions, one when ± is addition and one when it is subtraction.

$$x=\frac{-18±\sqrt{18^{2}}}{2\left(-1\right)}$$

Take the square root of 18^{2}.

$$x=\frac{-18±18}{2\left(-1\right)}$$

Multiply 2 times -1.

$$x=\frac{-18±18}{-2}$$

Now solve the equation x=\frac{-18±18}{-2} when ± is plus. Add -18 to 18.

$$x=\frac{0}{-2}$$

Divide 0 by -2.

$$x=0$$

Now solve the equation x=\frac{-18±18}{-2} when ± is minus. Subtract 18 from -18.

$$x=-\frac{36}{-2}$$

Divide -36 by -2.

$$x=18$$

Factor the original expression using ax^{2}+bx+c=a\left(x-x_{1}\right)\left(x-x_{2}\right). Substitute 0 for x_{1} and 18 for x_{2}.

$$-x^{2}+18x=-x\left(x-18\right)$$

Evaluate

$$x\left(18-x\right)$$