Here's the question you clicked on:
bless
Which is equal to 3[f(2x)] for f(x) = 3x^2+3/2? a.15/2 b. 81/2 c. 9x^2+9/2 d.18x^2+9
What part of this is giving you trouble?
when i try to substitute the f(x) to the 3[f(2x)] i can't get the answer
You substitute 2x into f(x), then multiply through the whole thing by 3.
Hmmm... and yes, if that is written right, I can see why that would not get an answer.
Is it supposed to be \(3[f(2)]\)?? Rather than 2x?
the answer is 108x^2 + 9/2?
Yes, as written, \(108x^2 + \cfrac{9}{2}\) would be correct.
if u want this answer then u should in question (3x)^2 instead of 3(x^2)
well there was another option to solve this problem : if the correct answer is not in the given choices, write you answer
Ah, yes... I see what Muhammad_Nauman_Umair is pointing out.
thanks for your help guys @Muhammad_Nauman_Umair and @e.mccormick
\((2x)^2=4x^2\) \(3\times 4x^2=12x^2\) \(3\times 12x^2=36x^2\) Which is what I got the first time... and when you said 108 I thought I had forgotten to multiply by 3.
\(36x^2 + \cfrac{9}{2}\) is what it should be.
36x^2+9/2