Quote:
Originally Posted by Xanatos903
The order of operations that he's talking about only applies when you've got two terms which can be combined in the same parentheses. 3x - x can be, since both are to the same power. But with the problems I gave you, it won't work that way. One thing that you can't do is take an x^2 down to an x. If it's an x^2, it stays that way for the entire problem (unless you're multiplying it by something with another x). Same with x, x^3, so on and so forth.
So just take the 3x and multiply it by everything in the parentheses directly beside it. You get 30x^2 and -36x^3. How I'm getting these numbers is that you multiply the coefficients (the numbers in front) first, and then add the number of X's together.
3x * 3x = 9x^2.
Repeat the same process for the -2x and what is in the parentheses right beside it, and you get -4x^2 - 8x
So, you've distributed the terms to their respective parentheses. Now you've got 4 terms that need to be stuck together so you can do a final simplification.
30x^2 -36x^3 -4x^2 - 8x.
Now, you can't just stick these all together because they've got x's in them. You have to combine the terms with the same exponents together to get your final answer. So let's look at the what we've got so far. There's only one term with an x, and only one term with an x^3, so we have to leave those as they are. But there are two terms with an x^2, so we can deal with those this way.
Keeping the same signs as they had previously, we get 30x^2 - 4x^2 = 26x^2. And that's as far as we can go, since we only have on term with an x^2, one with an x, and one with an x^3.
Bringing the other two terms that we couldn't do anything with down, we get our final answer, which is -36x^3 + 26x^2 - 8x.
Edit- It should be noted that unless we know what X is, simplifying beyond that is impossible. If we knew that x was 2, for instance, we could do it like this:
-36(2^3) + 26(2^2) - 8(2) = -200
But because we don't know what x is, we can't figure out what the final answer is. Just leave it as x^3, or whatever.
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Don't comprehend. I guess i will need to learn this hands on.
Getting taught by a teacher, by reading it doesn't make sense to me.
Here is another thing i'm having trouble with. Another homework packet.
Proportion in Area and volume.
A mixture of 2 parts sand 3 parts gravel is used to make 25 cubic yards of concrete.
How many cubic yards of each are needed?
(Hint: Solve two proportions.)
2 parts + 3 Parts = 5 parts.
Then 2:5 = x:25 (sand)
and 3:5 = x:25 (gravel)
