Date | November 2017 | Marks available | 4 | Reference code | 17N.3srg.hl.TZ0.2 |
Level | HL only | Paper | Paper 3 Sets, relations and groups | Time zone | TZ0 |
Command term | Verify | Question number | 2 | Adapted from | N/A |
Question
A, B and C are three subsets of a universal set.
Consider the sets P={1, 2, 3}, Q={2, 3, 4} and R={1, 3, 5}.
Represent the following set on a Venn diagram,
AΔB, the symmetric difference of the sets A and B;
Represent the following set on a Venn diagram,
A∩(B∪C).
For sets P, Q and R, verify that P∪(QΔR)≠(P∪Q)Δ(P∪R).
In the context of the distributive law, describe what the result in part (b)(i) illustrates.
Markscheme
A1
[1 mark]
Note: Accept alternative set configurations
A1
Note: Accept alternative set configurations.
[1 mark]
LHS:
QΔR={1, 2, 4, 5} (A1)
P∪(QΔR)={1, 2, 3, 4, 5} A1
RHS:
P∪Q={1, 2, 3, 4} and P∪R={1, 2, 3, 5} (A1)
(P∪Q)Δ(P∪R)={4, 5} A1
hence P∪(QΔR)≠(P∪Q)Δ(P∪R) AG
[4 marks]
the result shows that union is not distributive over symmetric difference A1R1
Notes: Award A1 for “union is not distributive” and R1 for “over symmetric difference”. Condone use of ∪ and Δ.
[2 marks]