Pre-Algebra Examples

$\sqrt{x + 25} + 5 = x$

Step 1

Subtract $5$ from both sides of the equation.

$\sqrt{x + 25} = x - 5$

Step 2

To remove the radical on the left side of the equation, square both sides of the equation.

${\sqrt{x + 25}}^{2} = {(x - 5)}^{2}$

Step 3

Simplify each side of the equation.

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Step 3.1

Use $\sqrt[n]{a^{x}} = a^{\frac{x}{n}}$ to rewrite $\sqrt{x + 25}$ as ${(x + 25)}^{\frac{1}{2}}$ .

${({(x + 25)}^{\frac{1}{2}})}^{2} = {(x - 5)}^{2}$

Step 3.2

Simplify the left side.

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Step 3.2.1

Simplify ${({(x + 25)}^{\frac{1}{2}})}^{2}$ .

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Step 3.2.1.1

Multiply the exponents in ${({(x + 25)}^{\frac{1}{2}})}^{2}$ .

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Step 3.2.1.1.1

Apply the power rule and multiply exponents, ${(a^{m})}^{n} = a^{m n}$ .

${(x + 25)}^{\frac{1}{2} \cdot 2} = {(x - 5)}^{2}$

Step 3.2.1.1.2

Cancel the common factor of $2$ .

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Step 3.2.1.1.2.1

Cancel the common factor.

${(x + 25)}^{\frac{1}{2} \cdot 2} = {(x - 5)}^{2}$

Step 3.2.1.1.2.2

Rewrite the expression.

${(x + 25)}^{1} = {(x - 5)}^{2}$

Step 3.2.1.2

Simplify.

$x + 25 = {(x - 5)}^{2}$

Step 3.3

Simplify the right side.

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Step 3.3.1

Simplify ${(x - 5)}^{2}$ .

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Step 3.3.1.1

Rewrite ${(x - 5)}^{2}$ as $(x - 5) (x - 5)$ .

$x + 25 = (x - 5) (x - 5)$

Step 3.3.1.2

Expand $(x - 5) (x - 5)$ using the FOIL Method.

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Step 3.3.1.2.1

Apply the distributive property.

$x + 25 = x (x - 5) - 5 (x - 5)$

Step 3.3.1.2.2

Apply the distributive property.

$x + 25 = x \cdot x + x \cdot - 5 - 5 (x - 5)$

Step 3.3.1.2.3

Apply the distributive property.

$x + 25 = x \cdot x + x \cdot - 5 - 5 x - 5 \cdot - 5$

Step 3.3.1.3

Simplify and combine like terms.

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Step 3.3.1.3.1

Simplify each term.

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Step 3.3.1.3.1.1

Multiply $x$ by $x$ .

$x + 25 = x^{2} + x \cdot - 5 - 5 x - 5 \cdot - 5$

Step 3.3.1.3.1.2

Move $- 5$ to the left of $x$ .

$x + 25 = x^{2} - 5 \cdot x - 5 x - 5 \cdot - 5$

Step 3.3.1.3.1.3

Multiply $- 5$ by $- 5$ .

$x + 25 = x^{2} - 5 x - 5 x + 25$

Step 3.3.1.3.2

Subtract $5 x$ from $- 5 x$ .

$x + 25 = x^{2} - 10 x + 25$

Step 4

Solve for $x$ .

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Step 4.1

Since $x$ is on the right side of the equation, switch the sides so it is on the left side of the equation.

$x^{2} - 10 x + 25 = x + 25$

Step 4.2

Move all terms containing $x$ to the left side of the equation.

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Step 4.2.1

Subtract $x$ from both sides of the equation.

$x^{2} - 10 x + 25 - x = 25$

Step 4.2.2

Subtract $x$ from $- 10 x$ .

$x^{2} - 11 x + 25 = 25$

Step 4.3

Subtract $25$ from both sides of the equation.

$x^{2} - 11 x + 25 - 25 = 0$

Step 4.4

Combine the opposite terms in $x^{2} - 11 x + 25 - 25$ .

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Step 4.4.1

Subtract $25$ from $25$ .

$x^{2} - 11 x + 0 = 0$

Step 4.4.2

Add $x^{2} - 11 x$ and $0$ .

$x^{2} - 11 x = 0$

Step 4.5

Factor $x$ out of $x^{2} - 11 x$ .

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Step 4.5.1

Factor $x$ out of $x^{2}$ .

$x \cdot x - 11 x = 0$

Step 4.5.2

Factor $x$ out of $- 11 x$ .

$x \cdot x + x \cdot - 11 = 0$

Step 4.5.3

Factor $x$ out of $x \cdot x + x \cdot - 11$ .

$x (x - 11) = 0$

Step 4.6

If any individual factor on the left side of the equation is equal to $0$ , the entire expression will be equal to $0$ .

$x = 0$

$x - 11 = 0$

Step 4.7

Set $x$ equal to $0$ .

$x = 0$

Step 4.8

Set $x - 11$ equal to $0$ and solve for $x$ .

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Step 4.8.1

Set $x - 11$ equal to $0$ .

$x - 11 = 0$

Step 4.8.2

Add $11$ to both sides of the equation.

$x = 11$

Step 4.9

The final solution is all the values that make $x (x - 11) = 0$ true.

$x = 0, 11$

Step 5

Exclude the solutions that do not make $\sqrt{x + 25} + 5 = x$ true.

$x = 11$