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C3 Modulus function question

Heya.
Could somone tell me if was attempting the correct solution for the question to 9 (iii).
http://www.ocr.org.uk/Images/79715-question-paper-unit-4723-core-mathematics-3.pdf

I substituted in the f(x)=20 and tried to find the discriminant didn't get very far, just wondered if this would work.
Thanks
Original post by SamuelN98

I substituted in the f(x)=20 and tried to find the discriminant didn't get very far, just wondered if this would work.
Thanks


Not really.

I start by sketching |f(x)|, then consider where there are three roots to |f(x)|=20. I.e. where must the horizontal line y=20 be on the graph in order to meet the curve at three points?
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SamuelN98
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Original post by ghostwalker
Not really.

I start by sketching |f(x)|, then consider where there are three roots to |f(x)|=20. I.e. where must the horizontal line y=20 be on the graph in order to meet the curve at three points?


I see, the first question makes sense now, gotta cross through the stationary point of the original curve?
Original post by SamuelN98
I see, the first question makes sense now, gotta cross through the stationary point of the original curve?


Correction.

It crosses through the the stationary point in the modulus curve. Which has the same x-value as the stationary point in the original curve.
(edited 7 years ago)

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