# Homework Help: Difference Quotient problem on test

1. Jan 7, 2010

### Tonik

I took a placement test and blew it away. (I tested into calculus, best possible placement for this test.) Everything was rather simple except for this problem which I cannot seem to get right. Can someone show me where I'm going wrong here?

1. The problem statement, all variables and given/known data
Use x2+2 in the Difference Quotient.

2. Relevant equations

3. The attempt at a solution
(x+h)2+2-(x2+2)

x2+xh+h2+2-x2-2

[STRIKE]x2[/STRIKE]+xh+h2[STRIKE]+2[/STRIKE][STRIKE]-x2[/STRIKE][STRIKE]-2[/STRIKE]

(xh+h2)/h

(x[STRIKE]h[/STRIKE]+h[STRIKE]2[/STRIKE])/[STRIKE]h[/STRIKE]

x+h

This answer was not a given choice. Any ideas where I'm messing up?
(I'm sure I making stupid mistake somewhere that I'm overlooking)

2. Jan 7, 2010

### pbandjay

There is an error in this line.

3. Jan 7, 2010

### Staff: Mentor

More specifically, you expanded (x + h)2 incorrectly. Also, you should use = between an expression on one line and the one on the following line.

4. Jan 7, 2010

### Tonik

ahh! okay....

x2+2xh+h2+2-x2-2

=

[STRIKE]x2[/STRIKE]+2xh+h2[STRIKE]+2-x2-2[/STRIKE]

=

2xh+h2/h

=

2x[STRIKE]h[/STRIKE]+h[STRIKE]2[/STRIKE]/[STRIKE]h[/STRIKE]

=

2x+h

That is the answer I chose since it was closest to my answer. You guys rock, thanks!