Solve x^2+191x+2709=0

$${ x }^{ 2 } +191x+2709=0$$

Solve for x

$$x=\frac{\sqrt{25645}-191}{2}\approx -15.429718372$$

$$x=\frac{-\sqrt{25645}-191}{2}\approx -175.570281628$$

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.

$$x^{2}+191x+2709=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 191 for b, and 2709 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-191±\sqrt{191^{2}-4\times 2709}}{2}$$

Square 191.

$$x=\frac{-191±\sqrt{36481-4\times 2709}}{2}$$

Multiply -4 times 2709.

$$x=\frac{-191±\sqrt{36481-10836}}{2}$$

Add 36481 to -10836.

$$x=\frac{-191±\sqrt{25645}}{2}$$

Now solve the equation x=\frac{-191±\sqrt{25645}}{2} when ± is plus. Add -191 to \sqrt{25645}.

$$x=\frac{\sqrt{25645}-191}{2}$$

Now solve the equation x=\frac{-191±\sqrt{25645}}{2} when ± is minus. Subtract \sqrt{25645} from -191.

$$x=\frac{-\sqrt{25645}-191}{2}$$

The equation is now solved.

$$x=\frac{\sqrt{25645}-191}{2} x=\frac{-\sqrt{25645}-191}{2}$$

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.

$$x^{2}+191x+2709=0$$

Subtract 2709 from both sides of the equation.

$$x^{2}+191x+2709-2709=-2709$$

Subtracting 2709 from itself leaves 0.

$$x^{2}+191x=-2709$$

Divide 191, the coefficient of the x term, by 2 to get \frac{191}{2}. Then add the square of \frac{191}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}+191x+\left(\frac{191}{2}\right)^{2}=-2709+\left(\frac{191}{2}\right)^{2}$$

Square \frac{191}{2} by squaring both the numerator and the denominator of the fraction.

$$x^{2}+191x+\frac{36481}{4}=-2709+\frac{36481}{4}$$

Add -2709 to \frac{36481}{4}.

$$x^{2}+191x+\frac{36481}{4}=\frac{25645}{4}$$

Factor x^{2}+191x+\frac{36481}{4}. In general, when x^{2}+bx+c is a perfect square, it can always be factored as \left(x+\frac{b}{2}\right)^{2}.

$$\left(x+\frac{191}{2}\right)^{2}=\frac{25645}{4}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x+\frac{191}{2}\right)^{2}}=\sqrt{\frac{25645}{4}}$$

Simplify.

$$x+\frac{191}{2}=\frac{\sqrt{25645}}{2} x+\frac{191}{2}=-\frac{\sqrt{25645}}{2}$$

Subtract \frac{191}{2} from both sides of the equation.

$$x=\frac{\sqrt{25645}-191}{2} x=\frac{-\sqrt{25645}-191}{2}$$