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Mathematics 31 Online
OpenStudy (anonymous):

Can someone help me solve this calc problem? It's attached.

OpenStudy (anonymous):

OpenStudy (anonymous):

Sample problem:

OpenStudy (anonymous):

you have the solution with the explanation, so what else do you need?

OpenStudy (anonymous):

I have a sample problem. I've tried applying the steps to the actual problem but it's confusing.

OpenStudy (anonymous):

So instead of substituting 6 and 1 into the v's, you'll substitute 5 and 2.

OpenStudy (anonymous):

The substitution takes place at the part where the expression is in square brackets. [ ]

OpenStudy (anonymous):

You'll plug in 5 first and evaluate. Keep that answer on the side somewhere. Then you'll go back to the square brackets again, plug in 2 and evaluate. Whatever you get as the answer, you'll subtract that from the answer you got when you plugged in 5.

OpenStudy (anonymous):

Can you wait while I do it, and tell me if it's correct?

OpenStudy (anonymous):

Yes.

OpenStudy (anonymous):

I got 77.5 when I plugged in 5.

OpenStudy (anonymous):

I got -7.5

OpenStudy (anonymous):

There's an extra negative sign next to the red negative sign. Ignore the extra one.

OpenStudy (anonymous):

\[{-3(5)^{2}\over 2}+6(5)\]

OpenStudy (anonymous):

Okay, so if I plug in 1, I'll get -3/2+8 = 6.5

OpenStudy (anonymous):

No. 4.5.

OpenStudy (anonymous):

Look at the equation I wrote above.

OpenStudy (anonymous):

What do you get when you evaluate that expression?

OpenStudy (anonymous):

Oh, I forgot to square it.

OpenStudy (anonymous):

Then I get: (-7.5+4.5) - (-3/2 +8) = -9.5 or -19/2.

OpenStudy (anonymous):

It's cool.

OpenStudy (anonymous):

It's not correct though.

OpenStudy (anonymous):

You're doing more than what it's asking for. The only values you're evaluating are 5 and 2. Not 6 and 1.

OpenStudy (anonymous):

6 and 1 are solely used in the example.

OpenStudy (anonymous):

You never answered my question. What do you get when you evaluate the expression I wrote above?

OpenStudy (anonymous):

-7.5

OpenStudy (anonymous):

Awesome. Now imagine the 5 is gone and a 2 is in its place in the expression above. What do you get now?

OpenStudy (anonymous):

Replace BOTH 5s with 2s. Not just the one on the left.

OpenStudy (anonymous):

6

OpenStudy (anonymous):

Perfect. Now the last step is subtracting that 6 from -7.5: -7.5 - 6 =

OpenStudy (anonymous):

-13.5

OpenStudy (anonymous):

Awesome : )

OpenStudy (anonymous):

But if you look at the sample problem, they subtracted another part too.

OpenStudy (anonymous):

They subtracted the value of the expression when a 1 was plugged in. We subtracted the value of the expression when a 2 was plugged in.

OpenStudy (anonymous):

I got -8 and it's still wrong.

OpenStudy (anonymous):

-8 on which problem?

OpenStudy (anonymous):

Ugh. It's + 8 not +6

OpenStudy (anonymous):

\[{-3v ^{2} \over 2}+8v\]

OpenStudy (anonymous):

Answer: -7.5 or -15/2

OpenStudy (anonymous):

Okay

OpenStudy (anonymous):

Sorry. I thought the expressions were the same in the example and actual problems.

OpenStudy (anonymous):

It's okay. Can you help with another problem?

OpenStudy (anonymous):

If you're not busy?

OpenStudy (anonymous):

Sure.

OpenStudy (anonymous):

OpenStudy (anonymous):

Sample:

OpenStudy (anonymous):

4/3

OpenStudy (anonymous):

Start off exactly as the example starts by dividing u and -4 by the square root of u. This gives you: \[\int\limits_{1}^{9}u ^{1/2}-4u ^{-1/2}\]

OpenStudy (anonymous):

Then integrate each term.

OpenStudy (anonymous):

\[[{2 \over 3}u ^{3/2}-8u ^{1/2}]\]

OpenStudy (anonymous):

Plug in 9 first, and evaluate. Plug in 1 afterwards, then evaluate. Subtract the second answer from the first one.

OpenStudy (anonymous):

Take care and don't forget to mark a Best Response. Thank you

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