Can anyone help me with this pre-cal please.

- anonymous

Can anyone help me with this pre-cal please.

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- anonymous

##### 1 Attachment

- anonymous

What's the question?

- anonymous

It's in the attachment

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## More answers

- anonymous

Which one(s) are you having trouble with?

- anonymous

All of them, but any help would be great.

- anonymous

So, the first one is:
a. Evaluate the expression 2a−3b/2 when a = −5 and b = −3
This means to plug the given values into the expression, and simplify.
According to order of operations, the division gets done *before* the subtraction, so the expression (when typeset) looks like this:
\[ 2a - \frac{3b}{2}\] Now, what do you get when you plug in -5 for a and -3 for b?

- anonymous

|dw:1442606735382:dw|
That's how it looks, and I plugged in a and b on the 2nd one

- anonymous

Okay, that's a different problem. So, we need to figure out which is the problem they're asking! What you had written was 2a - 3b/2, which is
\[2a - \frac{3b}{2}\]
What you put in your posted image is (2a-3b)/2, which is
\[\frac{2a-3b}{2}\]
They're different, and they'll give different answers.

- anonymous

Oh okay, I didn't know that. It's the second one then, (2a-3b)/2

- anonymous

Then you're off to a good start! Just start simplifying the numerator in \[\frac{2(-5) - 3(-3)}{2}\] ... what do you get?

- anonymous

|dw:1442607214084:dw|
Is that right?

- anonymous

You got it! Good! Done with the first one!

- anonymous

Awesome

- anonymous

Do you have an image for the second one? I suspect what appears in my attachment isn't the actual problem you want...

- anonymous

No, that's the actual problem, it's that exactly :)

- anonymous

Okay, then question (1b) is:
Simplify: 8y − 15 − 3(7 − y)
When you put this in regular math style, it looks like this:
\[ 8y - 15 - 3(7-y)\]
You need to do the multiplication first, so multiply out that last part, -3(7-y). What does that give you?

- anonymous

-15.89? or -21? If I did it right

- anonymous

We're on a different problem now ... there's no longer any a = -5 or b = -3 in sight! (That was just for problem 1a.) Now, just multiply this out:
\[-3(7-y)\]
Your answer will have a "y" in it!

- anonymous

-15.89y?

- anonymous

You need to use a distributive law: a(b+c) = ab + ac
Think: What's -3 times 7? (write it down)
Then think: what's -3 times -y? (write it down)

- anonymous

I'm curious .... where did you get the -15.89y from?

- anonymous

-3 times 7 is -21
-3 times -y is 5.10
I got -15.89 by putting -3(7-y) directly into the calculator... which is why I thought it was wrong

- anonymous

There's no NUMBER being plugged in for y in this problem.
-3 times -y is just 3y . (Remember: a negative times a negative is positive)
This problem isn't a calculator problem; it's an algebra problem (working with variables).

- anonymous

Ohh, okay. I was confused about that

- anonymous

Here's where we are so far:
\[\begin{align}
8y−15−3(7−y) &= 8y - 15 - 21 + 3y \cr
&= \text{ ??}
\end{align}\]
Now, you want to combine like terms. (Combine the number parts; combine the y terms.) What do you get?

- anonymous

Sorry my OpenStudy is acting up and being really slow.
Yes, 11y-33?

- anonymous

My computer just locked up! I had to close my whole browser and re-open and come back here? Might have been something going on at OpenStudy.
I like the 11y part. What's -15 - 21?

- anonymous

Oh, it's 36 then plus 3 is 39?

- anonymous

Unless it's negative 15 then it's 6 plus 3 which is 9

- anonymous

Remember: -15 - 21 means (-15) + (-21). Move to the left 15; move to the left 21 more; where do you end up? (You were *close* before when you got -33; just goofed up the arithmetic a bit.)

- anonymous

36

- anonymous

with a minus sign in front: -15 - 21 = -36.
Now, put it all together:
\[
8y−15−3(7−y) = 8y−15−21+3y = 11y - 36\]
and that's it!

- anonymous

Oh okay, got it! :) I added an extra 3 in my problem that's why I kept saying "plus 3" and yea, I forgot my minus sign. Thank you.

- anonymous

I'm just kind of having fun here today; I visited this site a few years ago, and didn't even know if it still existed. Clearly it does! It seems like a great resource for the math community. I may try to make regular appearances here! I've been working on a Precalculus course for years now, and I'm more than 2/3 of the way done:http://www.onemathematicalcat.org/Math/Precalculus_obj/tableOfContentsPreCalculus.htm
Lots of the stuff I was helping you with today is from my Algebra course (they always do algebra review in PreCalc):
http://www.onemathematicalcat.org/algebra_book/online_problems/table_of_contents.htm
You might want to check them out to see if they can help you. There's lots and lots of lots of practice with immediate feedback, so you can check your answers.
Well, I'd really love to stay and help you more right now, but I've got some other things I've got to do. Just re-post these as separate questions, and I'm sure someone will help you quickly! Have a wonderful day!

- anonymous

Okay, well thank you sooo much! You have a good day too!

- anonymous

Thanks! Bye!

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