[IGCSE] Need help with maths question Watch

Atham
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Hey there,
I am having troubles with question 12 (last question) in this PDF file.
The question is (if you cannot view the file):
The graph of y=f(x) where f(x)= ax^2 + bx + 3 crosses the x-axis at (-3,0) and (1,0). The y coordinate of the vertex is 4.

a) On the axes sketch the graph for y = f(x)
b) Find the values of a and b
c) Write down the range of f(x) when the domain is R.


Thanks in advance,

A.T.
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TenOfThem
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(Original post by Atham)
Hey there,
I am having troubles with question 12 (last question) in this PDF file.
The question is (if you cannot view the file):
The graph of y=f(x) where f(x)= ax^2 + bx + 3 crosses the x-axis at (-3,0) and (1,0). The y coordinate of the vertex is 4.

a) On the axes sketch the graph for y = f(x)
b) Find the values of a and b
c) Write down the range of f(x) when the domain is R.


Thanks in advance,

A.T.
Which part are you struggling with

What have you tried
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Atham
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All 3 as I don't know (remember) how to get a,b.
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TenOfThem
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(Original post by Atham)
All 3 as I don't know (remember) how to get a,b.
Put in the values for the 2 points that you have

Solve the simultaneous equations
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Atham
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What about the vertex point? Is that to help me draw the graph?

EDIT: Okay, I did that. I have a = -1, b = -2. Makes sense now. I was thinking about y = (x-h)^2 +k and all that stuff

What about question c) ?
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TenOfThem
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(Original post by Atham)


What about question c) ?
I would complete the square for that
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