Solve 9x^2-245x+500=0

$$9 { x }^{ 2 } -245x+500=0$$

Solve for x

$$x = \frac{20}{9} = 2\frac{2}{9} \approx 2.222222222$$

$$x=25$$

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.

$$9x^{2}-245x+500=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 9 for a, -245 for b, and 500 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-\left(-245\right)±\sqrt{\left(-245\right)^{2}-4\times 9\times 500}}{2\times 9}$$

Square -245.

$$x=\frac{-\left(-245\right)±\sqrt{60025-4\times 9\times 500}}{2\times 9}$$

Multiply -4 times 9.

$$x=\frac{-\left(-245\right)±\sqrt{60025-36\times 500}}{2\times 9}$$

Multiply -36 times 500.

$$x=\frac{-\left(-245\right)±\sqrt{60025-18000}}{2\times 9}$$

Add 60025 to -18000.

$$x=\frac{-\left(-245\right)±\sqrt{42025}}{2\times 9}$$

Take the square root of 42025.

$$x=\frac{-\left(-245\right)±205}{2\times 9}$$

The opposite of -245 is 245.

$$x=\frac{245±205}{2\times 9}$$

Multiply 2 times 9.

$$x=\frac{245±205}{18}$$

Now solve the equation x=\frac{245±205}{18} when ± is plus. Add 245 to 205.

$$x=\frac{450}{18}$$

Divide 450 by 18.

$$x=25$$

Now solve the equation x=\frac{245±205}{18} when ± is minus. Subtract 205 from 245.

$$x=\frac{40}{18}$$

Reduce the fraction \frac{40}{18} to lowest terms by extracting and canceling out 2.

$$x=\frac{20}{9}$$

The equation is now solved.

$$x=25 x=\frac{20}{9}$$

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.

$$9x^{2}-245x+500=0$$

Subtract 500 from both sides of the equation.

$$9x^{2}-245x+500-500=-500$$

Subtracting 500 from itself leaves 0.

$$9x^{2}-245x=-500$$

Divide both sides by 9.

$$\frac{9x^{2}-245x}{9}=-\frac{500}{9}$$

Dividing by 9 undoes the multiplication by 9.

$$x^{2}-\frac{245}{9}x=-\frac{500}{9}$$

Divide -\frac{245}{9}, the coefficient of the x term, by 2 to get -\frac{245}{18}. Then add the square of -\frac{245}{18} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}-\frac{245}{9}x+\left(-\frac{245}{18}\right)^{2}=-\frac{500}{9}+\left(-\frac{245}{18}\right)^{2}$$

Square -\frac{245}{18} by squaring both the numerator and the denominator of the fraction.

$$x^{2}-\frac{245}{9}x+\frac{60025}{324}=-\frac{500}{9}+\frac{60025}{324}$$

Add -\frac{500}{9} to \frac{60025}{324} by finding a common denominator and adding the numerators. Then reduce the fraction to lowest terms if possible.

$$x^{2}-\frac{245}{9}x+\frac{60025}{324}=\frac{42025}{324}$$

Factor x^{2}-\frac{245}{9}x+\frac{60025}{324}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x-\frac{245}{18}\right)^{2}=\frac{42025}{324}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x-\frac{245}{18}\right)^{2}}=\sqrt{\frac{42025}{324}}$$

Simplify.

$$x-\frac{245}{18}=\frac{205}{18} x-\frac{245}{18}=-\frac{205}{18}$$

Add \frac{245}{18} to both sides of the equation.

$$x=25 x=\frac{20}{9}$$