Official papers

Official 2018 Paper 2 · Q10

Paper 2Logic & proofFunctions & graphs

The function f(x)f(x) is defined for all real numbers.

Consider the following three conditions, where aa is a real constant:

  • I f(a−x)=f(a+x)f(a-x)=f(a+x) for all real xx.
  • II f(2a−x)=f(x)f(2a-x)=f(x) for all real xx.
  • III f(a−x)=f(x)f(a-x)=f(x) for all real xx.

Which of these conditions is/are necessary and sufficient for the graph of y=f(x)y=f(x) to have reflection symmetry in the line x=ax=a?

Condition I is necessary and sufficient Condition II is necessary and sufficient Condition III is necessary and sufficient
A yes yes yes
B yes yes no
C yes no yes
D yes no no
E no yes yes
F no yes no
G no no yes
H no no no
ABCDEFGH

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