Solve x+(x+2)(x+4)=50

$$x+(x+2)(x+4)=50$$

Solve for x

$$x = \frac{\sqrt{217} - 7}{2} \approx 3.865459931$$

$$x=\frac{-\sqrt{217}-7}{2}\approx -10.865459931$$

Steps Using the Quadratic Formula

Use the distributive property to multiply x+2 by x+4 and combine like terms.

$$x+x^{2}+6x+8=50$$

Combine x and 6x to get 7x.

$$7x+x^{2}+8=50$$

Subtract 50 from both sides.

$$7x+x^{2}+8-50=0$$

Subtract 50 from 8 to get -42.

$$7x+x^{2}-42=0$$

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.

$$x^{2}+7x-42=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 7 for b, and -42 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-7±\sqrt{7^{2}-4\left(-42\right)}}{2}$$

Square 7.

$$x=\frac{-7±\sqrt{49-4\left(-42\right)}}{2}$$

Multiply -4 times -42.

$$x=\frac{-7±\sqrt{49+168}}{2}$$

Add 49 to 168.

$$x=\frac{-7±\sqrt{217}}{2}$$

Now solve the equation x=\frac{-7±\sqrt{217}}{2} when ± is plus. Add -7 to \sqrt{217}.

$$x=\frac{\sqrt{217}-7}{2}$$

Now solve the equation x=\frac{-7±\sqrt{217}}{2} when ± is minus. Subtract \sqrt{217} from -7.

$$x=\frac{-\sqrt{217}-7}{2}$$

The equation is now solved.

$$x=\frac{\sqrt{217}-7}{2} x=\frac{-\sqrt{217}-7}{2}$$

Steps for Completing the Square

Use the distributive property to multiply x+2 by x+4 and combine like terms.

$$x+x^{2}+6x+8=50$$

Combine x and 6x to get 7x.

$$7x+x^{2}+8=50$$

Subtract 8 from both sides.

$$7x+x^{2}=50-8$$

Subtract 8 from 50 to get 42.

$$7x+x^{2}=42$$

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.

$$x^{2}+7x=42$$

Divide 7, the coefficient of the x term, by 2 to get \frac{7}{2}. Then add the square of \frac{7}{2} to both sides of the equation. This step makes the left hand side of the equation a perfect square.

$$x^{2}+7x+\left(\frac{7}{2}\right)^{2}=42+\left(\frac{7}{2}\right)^{2}$$

Square \frac{7}{2} by squaring both the numerator and the denominator of the fraction.

$$x^{2}+7x+\frac{49}{4}=42+\frac{49}{4}$$

Add 42 to \frac{49}{4}.

$$x^{2}+7x+\frac{49}{4}=\frac{217}{4}$$

Factor x^{2}+7x+\frac{49}{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}.

$$\left(x+\frac{7}{2}\right)^{2}=\frac{217}{4}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x+\frac{7}{2}\right)^{2}}=\sqrt{\frac{217}{4}}$$

Simplify.

$$x+\frac{7}{2}=\frac{\sqrt{217}}{2} x+\frac{7}{2}=-\frac{\sqrt{217}}{2}$$

Subtract \frac{7}{2} from both sides of the equation.

$$x=\frac{\sqrt{217}-7}{2} x=\frac{-\sqrt{217}-7}{2}$$