Supplying the missing numbers in open sentences from a set of given permissible substitutes - JSS1 Mathematics Lesson Note

This involves solving open sentences by finding the values of the variables from a given set of possible values.

Example 1: Consider the open sentence 

𝑥+3 = 8. If the set of permissible substitutes for 

𝑥 is {1, 2, 3, 5}, we need to find which of these values makes the sentence true.

If 𝑥= 1, then 

1+3=4 (False)

If 𝑥=2, then 

2+3=5 (False)

If 𝑥=3, then 

3+3=6 (False)

If 𝑥=5, then 

5+3=8 (True)

So, the missing number from the given set that makes the sentence true is 𝑥=5

Example 2: Consider the open sentence 

2𝑦−4= 6 with permissible substitutes for 

𝑦 being {2, 5, 6}.

If 𝑦=2, then 

2(2)−4=4−4=0(False)

If 𝑦= 5, then 

2(5)−4=10−4=6 (True)

If 𝑦=6, then 

2(6)−4=12−4=8 (False)

So, the missing number from the given set that makes the sentence true is 

𝑦=5.