Given f(x) = x^2-3x, find f(2x)

Please see your other post for my little rant about TELLING US WHERE YOU ARE STUCK.

Also, this really belongs in the pre-calc section.
 
I thought it equaled zero if it was not under a radical? What would it equal to?
 
Oh and I replied to the other post but its not showing up. I basically did the same thing I did here. Equalled everything not under a radical to zero and just solved it. If it was under a radical I did
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0.
 
srv96 said:
I thought it equaled zero if it was not under a radical? What would it equal to?
Click to expand...

You seem to be mixing up some different concepts here.

First, I suggest you review just what a function is and what independent and dependent variables are.

You then need to review what intercepts are and what domain is.

For your problem:

\(\displaystyle f(2x) = 4x^2-6x\)

If you want to find where the graph has x intercepts then you set this zero and solve for x.

No where in your question does it state you are looking for x-intercepts.

As for the radicals you mention: you need to first understand WHY we solve the inequality the way we do. Why cant we have a negative under a square root ? Why can we have a negative under a cube root? This is now of course referring to the domain of a function.

For example: What is the domain of:
\(\displaystyle p(x)=\sqrt{x+4}-3\)
\(\displaystyle h(x)=\sqrt[3]{x+4}-3\)

What are the x-intercepts of:
\(\displaystyle p(x)=\sqrt{x+4}-3\)
\(\displaystyle h(x)=\sqrt[3]{x+4}-3\)

In order to succeed in math you need to understand the why, and not just memorize a procedure/algorithm.
 
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