Find the Domain y=- square root of 9-x

$y = - \sqrt{9 - x}$

Step 1

Set the radicand in $\sqrt{9 - x}$ greater than or equal to $0$ to find where the expression is defined.

$9 - x \geq 0$

Step 2

Solve for $x$ .

Subtract $9$ from both sides of the inequality.

$- x \geq - 9$

Divide each term in $- x \geq - 9$ by $- 1$ and simplify.

Divide each term in $- x \geq - 9$ by $- 1$ . When multiplying or dividing both sides of an inequality by a negative value, flip the direction of the inequality sign.

$\frac{- x}{- 1} \leq \frac{- 9}{- 1}$

Simplify the left side.

Dividing two negative values results in a positive value.

$\frac{x}{1} \leq \frac{- 9}{- 1}$

Divide $x$ by $1$ .

$x \leq \frac{- 9}{- 1}$

Simplify the right side.

Divide $- 9$ by $- 1$ .

$x \leq 9$

Step 3

The domain is all values of $x$ that make the expression defined.

Interval Notation:

$(- \infty, 9]$

Set-Builder Notation:

${x | x \leq 9}$

Step 4

Find the Domain y=- square root of 9-x

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