Let Me Find f ( x ) f(x) First

Algebra Level 2

If f ( x 3 ) = 36 f\big(x^3\big) = 36 is true for all real x x , what is f ( x 2 ) f\big(x^2\big) ?


The answer is 36.

This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try refreshing the page, (b) enabling javascript if it is disabled on your browser and, finally, (c) loading the non-javascript version of this page . We're sorry about the hassle.

2 solutions

Margaret Zheng
Mar 21, 2016

Note that there is NOT a specific value given to x x . This means if f ( x 3 ) f(x^{3}) =36, then f ( a n y t h i n g ) f(anything) =36. Therefore, our answer to this question is 36 \boxed{36}

If f ( x 2 ) = 36 x R f(x^2)=36\quad \forall x\in \mathbb{R} then, f ( x 3 ) = 36 x R + { 0 } f(x^3)=36\quad \forall x\in \mathbb{R}^+ \cup\{0\} , but f ( x 3 ) 36 x R f(x^3)\neq36\quad \forall x\in \mathbb{R} in general.

A Former Brilliant Member - 5 years, 2 months ago

Log in to reply

Thank you and I will change this question once again:) it is not supposed to be difficult at all.

Margaret Zheng - 5 years, 2 months ago

Log in to reply

Why must we have f ( 1 ) = 36 f(-1) = 36 ?

Calvin Lin Staff - 5 years, 2 months ago

Log in to reply

@Calvin Lin Thank you for pointing out and I changed this problem the third time... I really have learned a lot from this problem!

Margaret Zheng - 5 years, 2 months ago

Smart change by the way!

A Former Brilliant Member - 5 years, 2 months ago

Log in to reply

@A Former Brilliant Member Thank you:DDD

Margaret Zheng - 5 years, 2 months ago

Well, then you should have mentioned that it is true for all x. From the given statement we know that there is a 'x' such that f ( x 2 ) = 36 f(x^2) = 36 .

Sudeep Salgia - 5 years, 2 months ago

Log in to reply

Thank you very much and I will add it to the question :D

Margaret Zheng - 5 years, 2 months ago
Ruben Janssens
Aug 1, 2020

A function that always has an output 36 when you insert anything, is the function f(x) = 36. So, logically, if you insert x^2 instead of x^3, the result will remain 36.

0 pending reports

×

Problem Loading...

Note Loading...

Set Loading...