## simple factoring: (x^2)(y^3)+xy

Simplificatation, evaluation, linear equations, linear graphs, linear inequalities, basic word problems, etc.
Tennise
Posts: 7
Joined: Sat Jun 06, 2009 7:12 am
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### simple factoring: (x^2)(y^3)+xy

I understand the numerical ones, but am having trouble with the variable ones...

It works in theory, and I can see how it would work, but when I substitute numbers for the variables, it doesn't work:
x = 2, y = 3
This was the expression: x2y3+xy
4*27+6 = 114

This was the answer: xy(xy2 + 1)
6(2*9) = 12*54 = 648
or...
6(18) = 108

Did I evaluate the equations wrong? I can't seem to get the same answer for them both...

jaybird0827
Posts: 21
Joined: Tue May 26, 2009 6:31 pm
Location: NC
Contact:

### Re: simple factoring: (x^2)(y^3)+xy

I understand the numerical ones, but am having trouble with the variable ones...

It works in theory, and I can see how it would work, but when I substitute numbers for the variables, it doesn't work:
x = 2, y = 3
This was the expression: x2y3+xy
4*27+6 = 114

This was the answer: xy(xy2 + 1)
6(2*9) = 12*54 = 648
or...
6(18) = 108

Did I evaluate the equations wrong? I can't seem to get the same answer for them both...
Let's look at
$xy(xy^2\,+\,1)$

Are you sure that you plugged everything in, correctly? We know that $xy = (2)(3)\,=\,6$ is correct.
Do you think that $114$ is the correct evaluation of $x^2y^3\,+\,xy$?
Also, what is the next multiple of 6 after 108?
Assuming that the answer to the first question is "yes", the answer to the second question should tell you that the value of the second factor $(xy^2\,+\,1)$ should be
$(next\,multiple\,of\,6\,after\,108)\div 6$.
Now, go back and re-evaluate
$xy(xy^2\,+\,1)$.

Last edited by jaybird0827 on Mon Jun 08, 2009 9:17 pm, edited 2 times in total.

Tennise
Posts: 7
Joined: Sat Jun 06, 2009 7:12 am
Contact:

### Re: simple factoring: (x^2)(y^3)+xy

I understand the numerical ones, but am having trouble with the variable ones...

It works in theory, and I can see how it would work, but when I substitute numbers for the variables, it doesn't work:
x = 2, y = 3
This was the expression: x2y3+xy
4*27+6 = 114

This was the answer: xy(xy2 + 1)
6(2*9) = 12*54 = 648
or...
6(18) = 108

Did I evaluate the equations wrong? I can't seem to get the same answer for them both...
Let's look at
$xy(xy^2\,+\,1)$

Are you sure that you plugged everything in, correctly? We know that $xy = (2)(3)\,=\,6$ is correct.
ah I see why: I ignored the +1 in the second expression! It's so easy to forget...

jaybird0827
Posts: 21
Joined: Tue May 26, 2009 6:31 pm
Location: NC
Contact:

### Re: simple factoring: (x^2)(y^3)+xy

ah I see why: I ignored the +1 in the second expression! It's so easy to forget...
You obviously got that before I finished editing. Awesome job!