Aloysius's answer to Cheryl's Secondary 4 A Maths Singapore question.

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Aloysius
Aloysius's answer
51 answers (Tutor Details)
1st
To prove that f(x) is a decreasing function, you need to prove that f'(x) (i.e. the gradient of the graph) is always less than 0. This shows that the graph is always downward sloping.