Solve -10000x^2+2080x-180=0

$$-10000 { x }^{ 2 } +2080x-180=0$$

Solve for x (complex solution)

$$x=\frac{\sqrt{449}i}{250}+\frac{13}{125}\approx 0.104+0.08475848i$$

$$x=-\frac{\sqrt{449}i}{250}+\frac{13}{125}\approx 0.104-0.08475848i$$

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.

$$-10000x^{2}+2080x-180=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute -10000 for a, 2080 for b, and -180 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-2080±\sqrt{2080^{2}-4\left(-10000\right)\left(-180\right)}}{2\left(-10000\right)}$$

Square 2080.

$$x=\frac{-2080±\sqrt{4326400-4\left(-10000\right)\left(-180\right)}}{2\left(-10000\right)}$$

Multiply -4 times -10000.

$$x=\frac{-2080±\sqrt{4326400+40000\left(-180\right)}}{2\left(-10000\right)}$$

Multiply 40000 times -180.

$$x=\frac{-2080±\sqrt{4326400-7200000}}{2\left(-10000\right)}$$

Add 4326400 to -7200000.

$$x=\frac{-2080±\sqrt{-2873600}}{2\left(-10000\right)}$$

Take the square root of -2873600.

$$x=\frac{-2080±80\sqrt{449}i}{2\left(-10000\right)}$$

Multiply 2 times -10000.

$$x=\frac{-2080±80\sqrt{449}i}{-20000}$$

Now solve the equation x=\frac{-2080±80\sqrt{449}i}{-20000} when ± is plus. Add -2080 to 80i\sqrt{449}.

$$x=\frac{-2080+80\sqrt{449}i}{-20000}$$

Divide -2080+80i\sqrt{449} by -20000.

$$x=-\frac{\sqrt{449}i}{250}+\frac{13}{125}$$

Now solve the equation x=\frac{-2080±80\sqrt{449}i}{-20000} when ± is minus. Subtract 80i\sqrt{449} from -2080.

$$x=\frac{-80\sqrt{449}i-2080}{-20000}$$

Divide -2080-80i\sqrt{449} by -20000.

$$x=\frac{\sqrt{449}i}{250}+\frac{13}{125}$$

The equation is now solved.

$$x=-\frac{\sqrt{449}i}{250}+\frac{13}{125} x=\frac{\sqrt{449}i}{250}+\frac{13}{125}$$

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.

$$-10000x^{2}+2080x-180=0$$

Add 180 to both sides of the equation.

$$-10000x^{2}+2080x-180-\left(-180\right)=-\left(-180\right)$$

Subtracting -180 from itself leaves 0.

$$-10000x^{2}+2080x=-\left(-180\right)$$

Subtract -180 from 0.

$$-10000x^{2}+2080x=180$$

Divide both sides by -10000.

$$\frac{-10000x^{2}+2080x}{-10000}=\frac{180}{-10000}$$

Dividing by -10000 undoes the multiplication by -10000.

$$x^{2}+\frac{2080}{-10000}x=\frac{180}{-10000}$$

Reduce the fraction \frac{2080}{-10000} to lowest terms by extracting and canceling out 80.

$$x^{2}-\frac{26}{125}x=\frac{180}{-10000}$$

Reduce the fraction \frac{180}{-10000} to lowest terms by extracting and canceling out 20.

$$x^{2}-\frac{26}{125}x=-\frac{9}{500}$$

Divide -\frac{26}{125}, the coefficient of the x term, by 2 to get -\frac{13}{125}. Then add the square of -\frac{13}{125} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}-\frac{26}{125}x+\left(-\frac{13}{125}\right)^{2}=-\frac{9}{500}+\left(-\frac{13}{125}\right)^{2}$$

Square -\frac{13}{125} by squaring both the numerator and the denominator of the fraction.

$$x^{2}-\frac{26}{125}x+\frac{169}{15625}=-\frac{9}{500}+\frac{169}{15625}$$

Add -\frac{9}{500} to \frac{169}{15625} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x^{2}-\frac{26}{125}x+\frac{169}{15625}=-\frac{449}{62500}$$

Factor x^{2}-\frac{26}{125}x+\frac{169}{15625}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x-\frac{13}{125}\right)^{2}=-\frac{449}{62500}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x-\frac{13}{125}\right)^{2}}=\sqrt{-\frac{449}{62500}}$$

Simplify.

$$x-\frac{13}{125}=\frac{\sqrt{449}i}{250} x-\frac{13}{125}=-\frac{\sqrt{449}i}{250}$$

Add \frac{13}{125} to both sides of the equation.

$$x=\frac{\sqrt{449}i}{250}+\frac{13}{125} x=-\frac{\sqrt{449}i}{250}+\frac{13}{125}$$