Intro to Evaluating Algebraic Expressions How to Evaluate Algebraic Expressions Math with Mr J

Welcome to math with Mr. In this video, I'm going to cover how to evaluate expressions. Now, to evaluate an expression, that just means to find the value of the expression. So, what it equals once you work through it. We will go through four examples. Two examples with one variable and two examples with two variables. These examples will help us learn how to evaluate expressions using substitution. They will set us up for success moving forward and give us strong foundation to build off of once we start evaluating more complex expressions. Let's jump into number one where we have + 22. Now, for numbers one and two, we need to evaluate these expressions or find the value of these expressions when equals 5. The first thing that we need to do, we need to replace or plug in the given value for the variable. That's called substitution. So, for number one, let's plug 5 in for and rewrite this expression. So, we have 5 + 22. Now, we can evaluate. So, we find out what this equals. 5 + 22 that equals 27. So, the value of this expression is 27 when equals 5. Let's move on to number two where we have 8x. Now, we have number next to variable. That means we are multiplying. So, this is 8 * Let's plug in and evaluate. So, we have * 5. 8 * 5 equals 40. So, the value of this expression is 40 when equals 5. Now, one thing do want to mention about number two, when we plug 5 in for make sure to use something to represent multiplication. used dot. We can't put those two numbers together, the 8 and the 5, to represent multiplication. That would look like 85. We can only put number next to variable to represent multiplication. So, something to keep in mind. Let's move on to numbers three and four where we have two variables and multiple operations. We will start with number three where we have 7b - So, 7 * - Let's start by plugging in the given values for and and we will rewrite this expression with those substitutions. So, 7 * Well, equals 9, so plug in 9 equals 10 so plug in 10. Now, we can evaluate. But, we have more than one operation. We have multiplication and subtraction. So, we need to use the order of operations, PEMDAS, in order to work through this. So, parentheses, exponents, multiplication and division, then addition and subtraction. Multiplication comes before subtraction, so let's multiply first. 7 * 9 equals 63. Then, we can bring down the subtraction sign and the 10. We end with 63 - 10 that equals 53. So, the value of this expression is 53 when equals 10 and equals 9. Lastly, let's move on to number four where we have + 18 / Let's plug in and evaluate. equals 10, so plug in 10 for + 18 / equals 9, so plug in 9 for We have addition and division. So, we need to go through the order of operations. Division comes before addition so let's divide first. 18 / 9 equals 2. Bring down the addition sign and the 10. So, we end with 10 + 2. 10 + equals 12. So, the value of this expression is 12 when equals 10 and equals 9. So, there you have it. There's an introduction to evaluating expressions using substitution. dropped links to more videos and examples down in the description. Those are great follow-ups to this introduction. hope that helped. Thanks so much for watching. Until next time. Peace.