# Thread: what is the value of x?

1. ## what is the value of x?

Find the value of x (either odd or even)..

5x^7 + 3x^4 = 241

2. ## Re: what is the value of x?

Originally Posted by rcs
Find the value of x (either odd or even)..

5x^7 + 3x^4 = 241

because if x = 1

then 5(1)^7 + 3(1)^4 = 8 which is not equal to 241

if x = 2

then
5(2)^7 + 3(2)^4 = 688 which is not equal to 241

What shall i do with this?

3. ## Re: what is the value of x?

your equation does not have an integer solution.

let $f(x)=5x^7+3x^4-241$

note $f(1)=-233$ and $f(2)=447$ ... since the function is continuous, there exists a value of $x$ in the interval $(1,2)$ where $f(x) = 0$

attached is a graph showing that single real zero

4. ## Re: what is the value of x?

Originally Posted by rcs
Find the value of x (either odd or even)..
5x^7 + 3x^4 = 241
Go here and enter your equation:
Wolfram|Alpha: Computational Knowledge Engine

5. ## Re: what is the value of x?

Originally Posted by rcs
Find the value of x (either odd or even)..

5x^7 + 3x^4 = 241
The reason I know your equation has no solutions in integers is A) if x is an odd integer,
then the left-hand side is even because is it the sum of two odd numbers, and B) if x
is an even integer, then the left-hand side is even because is it the sum of two even
numbers.

No specific values of x need to be substituted to do the problem. The corresponding
graph of f(x) = 5x^7 + 3x^4 need not be checked.