Solve 2x^2+6x-20=532

$$2 x ^ { 2 } + 6 x - 20 = 532$$

Solve for x

$$x = \frac{\sqrt{1113} - 3}{2} \approx 15.180827318$$

$$x=\frac{-\sqrt{1113}-3}{2}\approx -18.180827318$$

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.

$$2x^{2}+6x-20=532$$

Subtract 532 from both sides of the equation.

$$2x^{2}+6x-20-532=532-532$$

Subtracting 532 from itself leaves 0.

$$2x^{2}+6x-20-532=0$$

Subtract 532 from -20.

$$2x^{2}+6x-552=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 2 for a, 6 for b, and -552 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-6±\sqrt{6^{2}-4\times 2\left(-552\right)}}{2\times 2}$$

Square 6.

$$x=\frac{-6±\sqrt{36-4\times 2\left(-552\right)}}{2\times 2}$$

Multiply -4 times 2.

$$x=\frac{-6±\sqrt{36-8\left(-552\right)}}{2\times 2}$$

Multiply -8 times -552.

$$x=\frac{-6±\sqrt{36+4416}}{2\times 2}$$

Add 36 to 4416.

$$x=\frac{-6±\sqrt{4452}}{2\times 2}$$

Take the square root of 4452.

$$x=\frac{-6±2\sqrt{1113}}{2\times 2}$$

Multiply 2 times 2.

$$x=\frac{-6±2\sqrt{1113}}{4}$$

Now solve the equation x=\frac{-6±2\sqrt{1113}}{4} when ± is plus. Add -6 to 2\sqrt{1113}.

$$x=\frac{2\sqrt{1113}-6}{4}$$

Divide -6+2\sqrt{1113} by 4.

$$x=\frac{\sqrt{1113}-3}{2}$$

Now solve the equation x=\frac{-6±2\sqrt{1113}}{4} when ± is minus. Subtract 2\sqrt{1113} from -6.

$$x=\frac{-2\sqrt{1113}-6}{4}$$

Divide -6-2\sqrt{1113} by 4.

$$x=\frac{-\sqrt{1113}-3}{2}$$

The equation is now solved.

$$x=\frac{\sqrt{1113}-3}{2} x=\frac{-\sqrt{1113}-3}{2}$$

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.

$$2x^{2}+6x-20=532$$

Add 20 to both sides of the equation.

$$2x^{2}+6x-20-\left(-20\right)=532-\left(-20\right)$$

Subtracting -20 from itself leaves 0.

$$2x^{2}+6x=532-\left(-20\right)$$

Subtract -20 from 532.

$$2x^{2}+6x=552$$

Divide both sides by 2.

$$\frac{2x^{2}+6x}{2}=\frac{552}{2}$$

Dividing by 2 undoes the multiplication by 2.

$$x^{2}+\frac{6}{2}x=\frac{552}{2}$$

Divide 6 by 2.

$$x^{2}+3x=\frac{552}{2}$$

Divide 552 by 2.

$$x^{2}+3x=276$$

Divide 3, the coefficient of the x term, by 2 to get \frac{3}{2}. Then add the square of \frac{3}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}+3x+\left(\frac{3}{2}\right)^{2}=276+\left(\frac{3}{2}\right)^{2}$$

Square \frac{3}{2} by squaring both the numerator and the denominator of the fraction.

$$x^{2}+3x+\frac{9}{4}=276+\frac{9}{4}$$

Add 276 to \frac{9}{4}.

$$x^{2}+3x+\frac{9}{4}=\frac{1113}{4}$$

Factor x^{2}+3x+\frac{9}{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}.

$$\left(x+\frac{3}{2}\right)^{2}=\frac{1113}{4}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x+\frac{3}{2}\right)^{2}}=\sqrt{\frac{1113}{4}}$$

Simplify.

$$x+\frac{3}{2}=\frac{\sqrt{1113}}{2} x+\frac{3}{2}=-\frac{\sqrt{1113}}{2}$$

Subtract \frac{3}{2} from both sides of the equation.

$$x=\frac{\sqrt{1113}-3}{2} x=\frac{-\sqrt{1113}-3}{2}$$