word problem: If sides of square are decreased by 2cm, then

[BMWrider]

my wife goes to the university of Phoenix. She is struggling with algebra. We are pretty disappointed with the amount of help available there. Here's her problem that we cant figure out how to factor it

if the sides of a square are decreased by 2 cm, the area is decreased by 36 cm2. What were the dimensions of the original square?

we know the answer is 10cm. we figured it would be written like this. But how do we factor it?

x2 - (x-2)2 = 36

 

[royhaas]

You don't need to factor it. Expand and simplify, and the quadratic terms cancel.

 

[stapel]

my wife goes to the university of Phoenix....Here's her problem that we cant figure out how to factor it

It would probably be helpful if we could converse with the student herself. Please have your wife reply, showing all of her work and reasoning so far.

Thank you!

Eliz.

P.S. Welcome to FreeMathHelp!

 

[BMWrider]

Ok.. I guess I made a mistake saying the word "factor". "expand and simplify" or whatever the word is, we are stuck right where I stated. We aren't even sure the equation is written right.

As far as talking to the student herself and seeing her work, I'm typing exactly what she would. I should have just typed as my wife I guess. There would be absolutely no difference in what was typed if she had been the person typing or me as the scribe. I read other posts that parents had written for their children so I figured that was no problem.

We need help with the problem as stated. Otherwise why would we post here?

Thanks for the welcome.

 

[stapel]

I guess I made a mistake saying the word "factor". "expand and simplify" or whatever the word is

Well, "factor" is one thing that could be done with this quadratic, but not one that probably applies to this exercise. You almost certainly need to "solve" the equation, and apply the solutions to the word problem that generated it. :wink:

we are stuck right where I stated. We aren't even sure the equation is written right.

The equation looks good to me. To learn how to do the "expanding" mentioned earlier, you might want to try online lessons on how to multiply polynomials, since your book and/or class notes don't cover this (and since we cannot reasonable provide the classroom instruction within this environment).

I read other posts that parents had written for their children so I figured that was no problem.

Oops! It might have been better to read down through those threads: Parents (or friends, etc) posting for others generally, at some point, receive the same reply you did: The tutors need to interact with the actual student. :wink:

So please pass along to your wife the instructions that have been provided: She isn't ready to factor yet; she first needs to expand the squared bit; then she needs to simplify the left-hand side; then she needs to solve the resulting linear equation for the value of x; then she needs to apply this to the word problem. :!:

If she gets stuck, please have her reply showing all of her work and reasoning so far, so we can see how far she got in following the instructions, and see where she is having trouble. :idea:

Thank you!

Eliz.

 

[galactus]

\(\displaystyle \L\\(x-2)^{2}=x^{2}-36\)

Expand:

\(\displaystyle \L\\x^{2}-4x+4=x^{2}-36\)

Now, solve for x?

 

[BMWrider]

thanks galactus! Your written equation suddenly made sense in our mind. THAT'S the help we were looking for. The way we wrote the equation, while correct in theory, we just couldnt figure out.

Stapel, I appreciate your help too. I understand what your intentions are in saying the "student" needs to post her work on here herself. What you are perhaps overlooking is each situation is different and thus sometimes requires adjustment to the norm. My wife works a high level corporate job, and is traveling rather heavily right now unfortuneately. For my part, as her support to work towards her degree, is to help her however I can. If that means to be her scribe or investigator to help with areas where she get stuck, I do that. Believe me, wheither I type it or my wife types it, it's all exactly the same.

We are happy that we found this website!