91Ó°ÊÓ

Evaluating expressions might sound tricky, but it's a vital math skill you can master with practice. It means computing the value of the expression using the given values for the variables.
In our example, the expression is \(|-y| \text { for } y=-9\). First, understand that evaluating this expression means finding its numerical value.
Every expression has variables, constants, and operations. Start by clearly identifying what each symbol stands for. In this case, y is the variable that you'll evaluate.

Once you've identified the variables in the expression, the next step is substitution. Substitution means replacing each variable with its given value.
For the exercise at hand, you're given \({y=-9}\). Substitute this value into the original expression \(|-y|\). This step transforms the expression into \(|-(-9)|\). The negative sign bounces around the number, and this might be tricky but don’t worry!
Always handle one substitution at a time and double-check your replacements. This way, you reduce the chances of making an error.

Simplification comes after substitution and involves breaking down the expression to its simplest form. It generally requires performing arithmetic operations, combining like terms, or in our case, handling absolute values.
From the substitution step, you now have \(|-(-9)|\). Simplifying this, the double negative \(-(-9)\) becomes positive, so you’re left with \(|9|\).
The final simplification step involves evaluating the absolute value. Remember, the absolute value represents the distance of a number from zero, without considering direction. Therefore, \(|9| = 9\) since nine units from zero is always positive 9.
By combining these steps—understanding absolute values, substitution, and careful simplification—you can evaluate complex expressions with confidence!