Differentiate? x^2 = d/dx (x^2 - x)

[d1zz]

This question was on a multiple choice test and the answer I recieved was not the same as was on the list. I don't know any other way or direction to takle this question.

x^2= d/dx (x^2 - x)

I first differentiated the values in the brackets which yields 2x - 1. I then equated the equation to 0 and moved everything to the left side of the equal sign, and solved the equation. Now the answer was x = 1 but I recieved x = 1 AND x = -1.

Please help!

 

[pka]

You should have gotten the equation \(\displaystyle x^2 - 2x + 1 = 0.\)
It appears that you did not.
Go over your work.

 

[d1zz]

Yes I recieved that exact answer... and solving that answer yields: x=1 and x= -1

but the answer on the multiple choice list is x=1.

 

[galactus]

I get:

\(\displaystyle \L\\x^{2}=2x-1\)

\(\displaystyle \L\\x^{2}-2x+1=0\)

Factor:

\(\displaystyle (x-1)^{2}\)

1 is the answer. Multiplicity 2.

-1 would yield 4.

 

[d1zz]

Thank you for the clarification. I was thinking the exact same.

Thanks again.

 

[stapel]

This question was on a multiple choice test....

x^2 = d/dx (x^2 - x)

What were the instructions for this question?

Thank you.

Eliz.

 

[d1zz]

The question asked to solve for x.