I've got a take home test for a math108 class and would much rather watch The Adventures of Pete and Pete than struggle through this for the next 3 hours... I've only got about 10 problems left that I don't know how to do, plz help me anonymii.
1) "Simplify the expression. Express the answer so that all exponents are posetive. Whenever an exponent is 0 or negative, we assume that the base is not 0.
-3x^-3 "
Name:
Anonymous2007-05-07 3:53 ID:YGUigcgX
dude flip the base from x/1 to 1/x so you can write the exponent -3 as 3 instead. The -3 at the front just hangs there like a putz until it climbs on top to multiply with the 1.
Name:
Anonymous2007-05-07 4:11 ID:jMaEE6Dw
so... 1/(-3x^3) would be simplified completely?
2) "Factor (Prime if not factorable)
15x^4 +20x^2 +9x^2 -12"
Don't most of these problems usually go in a ^4,^3,^2 etc fashion? Type-o maybe? I dunnoz...
Name:
Anonymous2007-05-07 4:40 ID:YGUigcgX
wait, the -3 belongs on the top because it is not part of the base, it is just a thing multiplying to the power expression.
For the next one, you could insert 0x^3 and 0x if you'd like. But wait, is that really two terms with x^2? Those are like terms: add those first.
Name:
Anonymous2007-05-07 4:44 ID:YGUigcgX
When you have accomplished that, you will have a trinomial that you could pretend is the simpler form Ax^2 + Bx + C if that helps you figure out what you could do next.
Name:
Anonymous2007-05-07 4:46 ID:jMaEE6Dw
Okay, for 1) I got -3/(x^3)
Yeah, I'm not sure if it is supposed to be 20x^3 or not... oh well, I guess I can only assume it is to the ^2
Name:
Anonymous2007-05-07 4:55 ID:YGUigcgX
It's probably ^2, because what you get is factorable into a pair of binomials. Uh, the steps to get further are many - do know about what they call the method of decomposition for factoring a trinomial into a pair of binomial factors?
Name:
Anonymous2007-05-07 4:56 ID:jMaEE6Dw
alright, for 2) I've got (-5x^2+3)(-3x^2-4)... wut now?
Name:
Anonymous2007-05-07 5:03 ID:YGUigcgX
That won't do it since if you multiplied that out, you'd get 15x^4 + 11x^2 - 12
You are sort of getting there, just not with that
Name:
Anonymous2007-05-07 5:05 ID:jMaEE6Dw
15x^4 +20x^2 +9x^2 -12 should be
15x^4 +20x^2 -9x^2 -12
Oops...
Name:
Anonymous2007-05-07 5:17 ID:YGUigcgX
oh, ha then you got it fine, though it is an unusual configuration of negatives in your factors. There is a way to rewrite (-5x^2+3)(-3x^2-4) with less negatives and still get the same thing if you multiplied them out.
I got to get going now, tired.
Name:
Anonymous2007-05-07 5:19 ID:jMaEE6Dw
What would the solutions be though? +/-sqrt(.6) rite?
Name:
4tran2007-05-07 6:34 ID:UtbcN+OH
>>12
right, as long as you're ignoring the complex roots
Name:
Anonymous2007-05-07 7:22 ID:jMaEE6Dw
mkay, I watched a couple episodes of Pete & Pete...
3) "Perform the indicated operations and simplify the result. Leave the answer in factored form.
[x-(1/x^2)] / [x-(1/x^3)] "
wtf am i do?
Name:
4tran2007-05-07 8:54 ID:UtbcN+OH
>>14
multiply top and bottom by x^3, to get rid of the 1/x^3
Just factor... I came up with some huge trinomial that I didn't even want to fuck with :'(
Name:
Anonymous2007-05-07 14:41 ID:YGUigcgX
>>12
If you don't have an equation with = 0, or any equation for that matter, and you just have an expression, then all you needed to do was factor the expression. Nothing to actually solve for in that case.
Name:
Anonymous2007-05-07 15:01 ID:YGUigcgX
>>18
It won't factor like that because you can't cancel terms in that manner, example (a + b)/(a + c) does not equal b/c. You have to do some factoring work on the top and on the bottom, then look for matching factors top and bottom that you can then cancel. The top: x^4 - x has a common factor, so rewrite it, then you will see that one of the factors is a difference of cubes which has a way of factoring like this: a^3 – b^3 = (a – b)(a^2 + ab + b^2). The bottom: you have a difference of squares which has a way of factoring like this: a^2 - b^2 = (a - b)(a + b). Now because the first square is actually a power of degree 4, one of the factors will be another difference of squares of degree 2 that you can further factor.
>>19
You are probably meant to compress the expressing into a single fraction form. First factor all the fraction bottoms. (Notice that the second fraction has a difference of squares.) You will then need to make the fractions have a common denominator so that they all have the same factors on the bottom, allowing you to compress the expression into a single fraction. It is like when you have 1/6 + 1/8 and you have to multiply 1/6 by 4/4 and multiply 1/8 by 3/3 so that both fractions will have 24 on the bottom. But for you, you have to multiply top and bottom of each fraction by a binomial factor. Then you simplify the top of the fraction.