Question

Can anyone help me with this pre-cal please.

Answer 1

What's the question?

Answer 2

It's in the attachment

Answer 3

Which one(s) are you having trouble with?

Answer 4

All of them, but any help would be great.

Answer 5

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?

Answer 6

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

Answer 7

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.

Answer 8

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

Answer 9

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

Answer 10

Is that right?

Answer 11

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

Answer 12

Awesome

Answer 13

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

Answer 14

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

Answer 15

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?

Answer 16

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

Answer 17

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!

Answer 18

-15.89y?

Answer 19

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)

Answer 20

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

Answer 21

-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

Answer 22

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).

Answer 23

Ohh, okay. I was confused about that

Answer 24

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?

Answer 25

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

Answer 26

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?

Answer 27

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

Answer 28

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

Answer 29

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.)

Answer 30

36

Answer 31

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!

Answer 32

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.

Answer 33

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!

Answer 34

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

Answer 35

Thanks! Bye!