Solve x+8/x=-9

$$x + \frac { 8 } { x } = - 9$$

Solve for x

$$x=-8$$

$$x=-1$$

Steps Using Factoring

Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.

$$xx+8=-9x$$

Multiply x and x to get x^{2}.

$$x^{2}+8=-9x$$

Add 9x to both sides.

$$x^{2}+8+9x=0$$

Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.

$$x^{2}+9x+8=0$$

To solve the equation, factor x^{2}+9x+8 using formula x^{2}+\left(a+b\right)x+ab=\left(x+a\right)\left(x+b\right). To find a and b, set up a system to be solved.

$$a+b=9 ab=8$$

Since ab is positive, a and b have the same sign. Since a+b is positive, a and b are both positive. List all such integer pairs that give product 8.

$$1,8 2,4$$

Calculate the sum for each pair.

$$1+8=9 2+4=6$$

The solution is the pair that gives sum 9.

$$a=1 b=8$$

Rewrite factored expression \left(x+a\right)\left(x+b\right) using the obtained values.

$$\left(x+1\right)\left(x+8\right)$$

To find equation solutions, solve x+1=0 and x+8=0.

$$x=-1 x=-8$$

Steps Using Factoring By Grouping

Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.

$$xx+8=-9x$$

Multiply x and x to get x^{2}.

$$x^{2}+8=-9x$$

Add 9x to both sides.

$$x^{2}+8+9x=0$$

Rearrange the polynomial to put it in standard form. Place the terms in order from highest to lowest power.

$$x^{2}+9x+8=0$$

To solve the equation, factor the left hand side by grouping. First, left hand side needs to be rewritten as x^{2}+ax+bx+8. To find a and b, set up a system to be solved.

$$a+b=9 ab=1\times 8=8$$

Since ab is positive, a and b have the same sign. Since a+b is positive, a and b are both positive. List all such integer pairs that give product 8.

$$1,8 2,4$$

Calculate the sum for each pair.

$$1+8=9 2+4=6$$

The solution is the pair that gives sum 9.

$$a=1 b=8$$

Rewrite x^{2}+9x+8 as \left(x^{2}+x\right)+\left(8x+8\right).

$$\left(x^{2}+x\right)+\left(8x+8\right)$$

Factor out x in the first and 8 in the second group.

$$x\left(x+1\right)+8\left(x+1\right)$$

Factor out common term x+1 by using distributive property.

$$\left(x+1\right)\left(x+8\right)$$

To find equation solutions, solve x+1=0 and x+8=0.

$$x=-1 x=-8$$

Steps Using the Quadratic Formula

Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.

$$xx+8=-9x$$

Multiply x and x to get x^{2}.

$$x^{2}+8=-9x$$

Add 9x to both sides.

$$x^{2}+8+9x=0$$

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.

$$x^{2}+9x+8=0$$

This equation is in standard form: ax^{2}+bx+c=0. Substitute 1 for a, 9 for b, and 8 for c in the quadratic formula, \frac{-b±\sqrt{b^{2}-4ac}}{2a}.

$$x=\frac{-9±\sqrt{9^{2}-4\times 8}}{2}$$

Square 9.

$$x=\frac{-9±\sqrt{81-4\times 8}}{2}$$

Multiply -4 times 8.

$$x=\frac{-9±\sqrt{81-32}}{2}$$

Add 81 to -32.

$$x=\frac{-9±\sqrt{49}}{2}$$

Take the square root of 49.

$$x=\frac{-9±7}{2}$$

Now solve the equation x=\frac{-9±7}{2} when ± is plus. Add -9 to 7.

$$x=-\frac{2}{2}$$

Divide -2 by 2.

$$x=-1$$

Now solve the equation x=\frac{-9±7}{2} when ± is minus. Subtract 7 from -9.

$$x=-\frac{16}{2}$$

Divide -16 by 2.

$$x=-8$$

The equation is now solved.

$$x=-1 x=-8$$

Steps for Completing the Square

Variable x cannot be equal to 0 since division by zero is not defined. Multiply both sides of the equation by x.

$$xx+8=-9x$$

Multiply x and x to get x^{2}.

$$x^{2}+8=-9x$$

Add 9x to both sides.

$$x^{2}+8+9x=0$$

Subtract 8 from both sides. Anything subtracted from zero gives its negation.

$$x^{2}+9x=-8$$

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

$$x^{2}+9x+\left(\frac{9}{2}\right)^{2}=-8+\left(\frac{9}{2}\right)^{2}$$

Square \frac{9}{2} by squaring both the numerator and the denominator of the fraction.

$$x^{2}+9x+\frac{81}{4}=-8+\frac{81}{4}$$

Add -8 to \frac{81}{4}.

$$x^{2}+9x+\frac{81}{4}=\frac{49}{4}$$

Factor x^{2}+9x+\frac{81}{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}.

$$\left(x+\frac{9}{2}\right)^{2}=\frac{49}{4}$$

Take the square root of both sides of the equation.

$$\sqrt{\left(x+\frac{9}{2}\right)^{2}}=\sqrt{\frac{49}{4}}$$

Simplify.

$$x+\frac{9}{2}=\frac{7}{2} x+\frac{9}{2}=-\frac{7}{2}$$

Subtract \frac{9}{2} from both sides of the equation.

$$x=-1 x=-8$$