[purple-owl]

Hey everyone

Would really REALLY REALLY REALLY appreciate if you could help me understand this question and find the answer!!!

The following functions are defined for all real values of values. Find the range of f(x) = 9-2x^2

Thank you!!!!!

[Intriguing Alias]

(Original post by purple-owl)
Hey everyone

Would really REALLY REALLY REALLY appreciate if you could help me understand this question and find the answer!!!

The following functions are defined for all real values of values. Find the range of f(x) = 9-2x^2

Thank you!!!!!

It means that you can use any real value of x (if you don't do further maths - consider this 'you can use all values of x').

Then it's asking what values of f(x) can you get out. Are there any values that you CAN'T get?

[notnek]

is always so what is the maximum value of the function?

And as x gets bigger, f(x) gets smaller but is there a minimum?

It may help you to think about the graph of the function.

[purple-owl]

It's so much easier when you have the actual graph for it but the thing is I don't know how to draw the graph for that function! (and I won't have WolframAlpha in the exam either)

[notnek]

(Original post by purple-owl)
It's so much easier when you have the actual graph for it but the thing is I don't know how to draw the graph for that function! (and I won't have WolframAlpha in the exam either)

You should know how to draw quadratics. A quadratic with a positive x^2 term generates a U shape or "happy face" parabola and a negative x^2 quadratic (like the one in your question) is a "sad face" parabola.

Every "sad face" quadratic has a maximum so think about what I said in my last post to determine where it is.