Evaluating Expressions

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by Anjie Julseth15 views·Updated Nov 3, 2020
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  1. Hi guys, Miss Joel.
  2. Seth Here and today we're gonna talk about evaluating algebraic
  3. expressions. An expression is not in equation because it does
  4. not have an equal sign.
  5. There are two types of expressions.
  6. Five plus 84 that's New Miracle and three X plus
  7. 10. That's as algebraic notice.
  8. There are no equal signs in these expressions, so they're
  9. not equations.
  10. A new miracle expression contains Onley numbers and symbols.
  11. No letters, so five times three plus eight That would
  12. be new.
  13. Miracle and algebraic expression.
  14. Contains Onley numbers, symbols and variables.
  15. It is sometimes referred to as a variable expression, so
  16. the product of three and X is three and X
  17. smashed together.
  18. That means three times X, the some of em and
  19. eight is M plus eight.
  20. The difference of our and two is R minus two.
  21. Again, those air algebraic expressions.
  22. Okay, what is a variable?
  23. A variable represents an unknown value so it can meet
  24. any letter in the whole alphabet.
  25. And it could be any number in the whole wide
  26. world that it could represent.
  27. It can represent multiple numbers.
  28. Eso we say it varies.
  29. It's a variable.
  30. So for plus x x is the variable because it's
  31. the unknown value.
  32. Five. Why?
  33. Why is the variable is unknown?
  34. 10. Minus question.
  35. Mark 20 over.
  36. Smiley face.
  37. So here we have examples that aren't even letters that
  38. are just symbols.
  39. Ah, variable can be any letter of the alphabet, since
  40. it represents an unknown.
  41. Sometimes variables are Greek letters to that's kind of cool.
  42. Okay, expressions, word phrases.
  43. Phrases for multiplication are the product of five and a
  44. numbers. See, so you could put five dot C or
  45. five and see just smashed together with nothing in between
  46. them. Seven times and number T seven dot t or
  47. seven smashed together with tea and then six multiplied by
  48. a number.
  49. D six times D with the dot there or six
  50. smashed together with D.
  51. The placement rule for multiplication is the product of five
  52. and a number C five dot c or five.
  53. See, you always write the variable after the number.
  54. That's why we had five first and then see seven
  55. first and then T six first and then D evaluate
  56. means to find the value of an algebraic expression by
  57. substituting numbers in for variables.
  58. So example.
  59. For example, if I say M equals two and then
  60. I have the expression six plus m.
  61. I would plug the to infer M and six plus
  62. two is eight.
  63. So I'm substituting or plugging in the new miracle value.
  64. Okay, so here's another example.
  65. If R equals 37 plus our would equal what seven
  66. plus three because you replace the are with 37 plus
  67. three is 10.
  68. Okay, evaluate the variable expression when n equals six.
  69. Okay, So if n plus eight is the expression, then
  70. where you replace end with +66 plus eight now becomes
  71. 14. If the new expression is and minus two Look,
  72. it's the same letter and the same value.
  73. But we have a new expression and minus two, we
  74. plug in the 66 minus two is four.
  75. Evaluate just means solved by substitution.
  76. Okay, here's another example.
  77. So when n equals 63 times N would be three
  78. times six, you replace the end with a six on
  79. that equals 18.
  80. And then in over six, for example, number four would
  81. be 6/6 because you replace the end with a 6
  82. 6/6 is one.
  83. Now, we've just been using the letter end, but you
  84. can use any single letter in the whole alphabet.
  85. Okay, here the algebraic Express evaluate the algebraic expression when
  86. n equals eight.
  87. So if we have number 1 56 over n, that's
  88. the Samos 56/8, which is seven.
  89. And then number 2 20 minus n replaced.
  90. The end within eight would be 20 minus eight, which
  91. is 12.
  92. Okay, here we're using A and B instead of end.
  93. And that's okay too.
  94. So we have three times a because it smashed together.
  95. Plus B, if a is three, replace the A with
  96. three. And if b is four, replace the B with
  97. four. So we have three from the original expression times
  98. three. That that's what we replace the A with plus
  99. four what we replace the be with.
  100. So three times three is nine plus four is 13.
  101. Example Number two.
  102. We have to be minus a substitute for and for
  103. B and three.
  104. And for a two times four is eight minus three
  105. is five.
  106. Upsy daisies went too far.
  107. Okay, Example.
  108. Three to a B.
  109. A s, three b s.
  110. Four. That means they're all smashed together.
  111. So it's two times a times B.
  112. So two times three times four when you substitute in
  113. two times three or six and then times four is
  114. 24 and then we have number 45 plus a B
  115. A B or smashed together.
  116. That means that they're times so five plus three times
  117. four when you substitute in the three and the four
  118. for A and B so five plus three times four
  119. is 12 5 plus 12 17.
  120. Okay, now we're gonna use X and y.
  121. So the first example is three X over y instead
  122. of three.
  123. We put in a 53 times five is 15.
  124. Instead of why we put in a 3 15 divided
  125. by three is five.
  126. Okay, now it gets trickier.
  127. We have X to the power of two plus y
  128. to the power of to You can also say squared
  129. X squared plus y squared.
  130. So we plug in a five instead of X and
  131. we plug in a three instead of why five squared
  132. means five times +55 times itself twice.
  133. So five times five is 25.
  134. Three squared equals three times itself.
  135. So three times three is 9 25 plus nine is
  136. 34. All right, so you should definitely write this down
  137. in your notes, please.
  138. Types of expressions and expression is not an equation because
  139. it does not have an equal sign.
  140. There are two types of expressions.
  141. Numerical expressions contain Onley numbers and symbols.
  142. For example, five times three plus four algebraic expressions contain
  143. numbers, symbols and variables, also known as variable expressions.
  144. So, for example, M plus eight and then lastly, please
  145. write this down.
  146. A variable is a letter or symbol that represents a
  147. number, for example X.
  148. You can always pause this video so you could write
  149. this stuff down.
  150. Okay? And then there's one more thing for you to
  151. write down.
  152. Evaluate if X equals three and y equals force to
  153. evaluate means to solve you.
  154. Um, so we have two times parentheses.
  155. That's the called the quantity X plus y quantity squared.
  156. And then you show the substitution.
  157. You replace X with three.
  158. And why with four.
  159. Okay, then you do your work.
  160. We do parentheses.
  161. First three plus 47 Then we do exponents.
  162. Seven squared is 49.
  163. Then we multiply by 2 98.
  164. Show your work one step at a time, and we
  165. have no equal sites, and, uh, that's all Thank you
  166. for tuning in.