Substitution Substitution When we replace a letter with a value it is called substitution. Here are five expressions. Key Words Substitute Evaluate Evaluate these expressions when a = 5, b = 2 and c= -1. 1) a + b + c 2) 3a + 2c 3) a(b + c) 4) abc 2 – a c 5) b What is the value of each of these expressions if n=8 8 What is the value of each of these expressions if n = -3 -3 Answers What is the value of each of these expressions if n=8 8 What is the value of each of these expressions if n = -3 -3 When we replace a letter with a value it is called substitution. Work out the value of these expressions when:a = -2 b=5 c=8 i) ii) iii) iv) b+5= c–b= ab = 3b + 2 = v) vi) 5(a + b)= 7b = 4 vii) (a+2b)(c-4) Plenary Return to your 5 expressions. Attempt the ones you could not do at the start Evaluate these expressions when a = 5, b = 2 and c =1. 1) a + b + c 2) 3a + 2c What does substitution mean? 3) a(b + c) 4) abc Can you write your own statement? 2 – c a 5) b Substitution is …………………………… This is a magic square. Work out the magic number when:1) 2) 3) a = 8, b = 3 and c = 4 a = 10, b = 4 and c = 1 a = 14, b = 9 and c = 2 Title Date To link algebraic and written representations of formulae 10-Jan-21 Expression Equation 3n + 1 = 10 Term 2n Which word matches which star? Can you explain your answer? n+6 Activity Challenge Once you have worked out the value of each expression using n = 4 ….. line the n expression cards up in value from smallest to largest and write down. Is there a number that would change the order of the cards? Try some different ones to see! Card Set 1 – Core Expressions 2n n 5 n+8 n + 10 Multiply n by 2, then add 1 Multiply n by 10 n2 Halve n. n take away 5. n-5 Add 10 to n. Times n by 2, then add 1. Add 12 to n. Add 1 to n, then times by 2. Multiply n by itself. Double n. Times n by 4, then minus 2. Take n away from 20. Divide n by 5. Add 8 to n 4n - 2 20 - n n 2n + 1 2 n + 12 2( n + 1) 5n Card Set 2 – Explanations in words 10n Square n. Copies in white Times n by 5. Easier Harder 40 250 n=5 How many different expressions can you find to make the value in the cloud? Substitution Bingo Aim: Full House Grid: 9 Grid Play: Calculate value & cross it off Numbers to Use • • • • 2 3 30 32 81 4 16 6 25 -2 19 55 -18 7 -8 34 Question • 3a + 2b = ? • when a=4 and b=2 Question • 4a - b = ? • when a=3 and b=5 Question • a - 6b = ? • when a=10 and b=2 Question • 3a + b = ? 2 • when a=5 and b= -3 Question • a2 + 5b = ? • when a=5 and b=6 Question • (a+b)2 = ? • when a=7 and b=2 Question • 2(a-b) = ? a • when a=20 and b= -10 Question • 3a - 2b = ? • when a= -4 and b=3 Question • 2a2 = ? • when a=4 Question • 3b + 4a - b = ? • when a=5 and b=7 Question • (a+2b)x6 = ? • when a=7 and b= -1 Question • 0.5a + b = ? • when a=14 and b= -5 Question • ¾a + ½b = ? • when a=20 and b=8 Question • a2 + b2 = ? • when a=4 and b=3 Question • 2a-b = ? b • when a=5 and b=2 Question • a3 = ? • when a= -2 In today’s lesson I substituted values into expressions. Substitute means …………….. An example of this is ……………..