Prelim Quadratics Question (1 Viewer)

Wonder

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From Cambridge Year 11 3U, Exercise 8A

(Not the explain part, just part d.) Thanks in advance! :)
 

iBibah

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f(-2)=1

f(x)=ax(x-0) - Only passes through x axis at origin
=ax^2

f'(x)=2ax
f'(-2)=2(-2)a=1

a=-1/4

therefore f(x)=-1/4x^2
 

Wonder

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Got it, thanks for your help!
 
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Wonder

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Wait, confused again. How did you get f(x)=2ax?
 

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