Solve 0.0009-0.18x+8x^2=0

$$0.0009 - 0.18 x + 8 x ^ { 2 } = 0$$

Solve for x

$$x=0.015$$

$$x=0.0075$$

Steps Using the Quadratic Formula

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.

$$8x^{2}-0.18x+0.0009=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 8 for a, -0.18 for b, and 0.0009 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-\left(-0.18\right)±\sqrt{\left(-0.18\right)^{2}-4\times 8\times 0.0009}}{2\times 8}$$

Square -0.18 by squaring both the numerator and the denominator of the fraction.

$$x=\frac{-\left(-0.18\right)±\sqrt{0.0324-4\times 8\times 0.0009}}{2\times 8}$$

Multiply -4 times 8.

$$x=\frac{-\left(-0.18\right)±\sqrt{0.0324-32\times 0.0009}}{2\times 8}$$

Multiply -32 times 0.0009.

$$x=\frac{-\left(-0.18\right)±\sqrt{0.0324-0.0288}}{2\times 8}$$

Add 0.0324 to -0.0288 by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x=\frac{-\left(-0.18\right)±\sqrt{0.0036}}{2\times 8}$$

Take the square root of 0.0036.

$$x=\frac{-\left(-0.18\right)±\frac{3}{50}}{2\times 8}$$

The opposite of -0.18 is 0.18.

$$x=\frac{0.18±\frac{3}{50}}{2\times 8}$$

Multiply 2 times 8.

$$x=\frac{0.18±\frac{3}{50}}{16}$$

Now solve the equation x=\frac{0.18±\frac{3}{50}}{16} when ± is plus. Add 0.18 to \frac{3}{50} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x=\frac{\frac{6}{25}}{16}$$

Divide \frac{6}{25} by 16.

$$x=\frac{3}{200}$$

Now solve the equation x=\frac{0.18±\frac{3}{50}}{16} when ± is minus. Subtract \frac{3}{50} from 0.18 by finding a common denominator and subtracting the numerators. Then reduce the fraction to lowest terms if possible.

$$x=\frac{\frac{3}{25}}{16}$$

Divide \frac{3}{25} by 16.

$$x=\frac{3}{400}$$

The equation is now solved.

$$x=\frac{3}{200} x=\frac{3}{400}$$

Steps for Completing the Square

Quadratic equations such as this one can be solved by completing the square. In order to complete the square, the equation must first be in the form x^{2}+bx=c.

$$8x^{2}-0.18x+0.0009=0$$

Subtract 0.0009 from both sides of the equation.

$$8x^{2}-0.18x+0.0009-0.0009=-0.0009$$

Subtracting 0.0009 from itself leaves 0.

$$8x^{2}-0.18x=-0.0009$$

Divide both sides by 8.

$$\frac{8x^{2}-0.18x}{8}=-\frac{0.0009}{8}$$

Dividing by 8 undoes the multiplication by 8.

$$x^{2}+\left(-\frac{0.18}{8}\right)x=-\frac{0.0009}{8}$$

Divide -0.18 by 8.

$$x^{2}-0.0225x=-\frac{0.0009}{8}$$

Divide -0.0009 by 8.

$$x^{2}-0.0225x=-0.0001125$$

Divide -0.0225, the coefficient of the x term, by 2 to get -0.01125. Then add the square of -0.01125 to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}-0.0225x+\left(-0.01125\right)^{2}=-0.0001125+\left(-0.01125\right)^{2}$$

Square -0.01125 by squaring both the numerator and the denominator of the fraction.

$$x^{2}-0.0225x+0.0001265625=-0.0001125+0.0001265625$$

Add -0.0001125 to 0.0001265625 by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x^{2}-0.0225x+0.0001265625=0.0000140625$$

Factor x^{2}-0.0225x+0.0001265625. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x-0.01125\right)^{2}=0.0000140625$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x-0.01125\right)^{2}}=\sqrt{0.0000140625}$$

Simplify.

$$x-0.01125=\frac{3}{800} x-0.01125=-\frac{3}{800}$$

Add 0.01125 to both sides of the equation.

$$x=\frac{3}{200} x=\frac{3}{400}$$