What if you wanted to evaluate the expression

### Using a Calculator

A calculator, especially a graphing calculator, is a very useful tool in evaluating algebraic expressions. A graphing calculator follows the order of operations, PEMDAS. In this section we will explain two ways of evaluating expressions with a graphing calculator.

#### Use a graphing calculator to solve the problems

**Method #1** This method is the direct input method. After substituting all values for the variables, you type in the expression, symbol for symbol, into your calculator.

*Evaluate* *when*

*Substitute the value* *into the expression.*

The potential error here is that you may forget a sign or a set of parentheses, especially if the expression is long or complicated. Make sure you check your input before writing your answer. An alternative is to type in the expression in appropriate chunks – do one set of parentheses, then another, and so on.

**Method #2** This method uses the STORE function of the Texas Instrument graphing calculators, such as the TI-83, TI-84, or TI-84 Plus.

*First, store the value x=−3 in the calculator. Type* -3

**[STO]**

*The letter*x can be entered using the

**[VAR]**

*button or*

**[ALPHA] + [STO]**).

*Then type in the expression in the calculator and press*

**[ENTER]**.

*The answer is*

Note: On graphing calculators there is a difference between the minus sign and the negative sign. When we stored the value negative three, we needed to use the negative sign, which is to the left of the **[ENTER]** button on the calculator. On the other hand, to perform the subtraction operation in the expression we used the minus sign. The minus sign is right above the plus sign on the right.

#### You can also use a graphing calculator to evaluate expressions with more than one variable.

*Evaluate the expression:* *for*

Store the values of **[STO]** **[STO]** **[ALPHA] + [KEY]**. Input the expression in the calculator. When an expression shows the division of two expressions, be sure to use parentheses: (numerator) **[ENTER]** to obtain the answer

### Example

*Evaluate the expression* *for*

Store the values of **[STO]** **[STO]** **[ALPHA] + [KEY]**. Input the expression in the calculator. When an expression shows the division of two expressions, be sure to use parentheses: (numerator) **[ENTER]** to obtain the answer

### Review

In 1-5, evaluate each expression using a graphing calculator.

x2+2x−xy whenx=250 andy=−120 (xy−y4)2 whenx=0.02 andy=−0.025 x+y−zxy+yz+xz whenx=12, y=32 , andz=−1 (x+y)24x2−y2 whenx=3 andy=−5d - The formula to find the volume of a spherical object (like a ball) is
V=43(π)r3 , wherer= the radius of the sphere. Determine the volume for a grapefruit with a radius of 9 cm.

In 6-9, insert parentheses in each expression to make a true equation.

5−2⋅6−4+2=5 - \begin{align*}12 \div 4 + 10 - 3 \cdot 3 + 7 = 11\end{align*}
- \begin{align*}22 - 32 - 5 \cdot 3 - 5 = 30\end{align*}
- \begin{align*}12 - 8 - 4 \cdot 5 = -8\end{align*}

### Answers for Review Problems

To see the Review answers, open this PDF file and look for section 1.5.