Test Review Question

[jiblition]

Hello,

I really need some help with a couple questions for this test review if anyone could help I'd greatly appreciate it.

"Evaluate the following indefinite integral by using the given substitution to reduce the integral to standard form."

(integral) 7(7x+21)^9 dx = .....?

Can someone show how to do this in logical steps please

 

[srmichael]

Hello,

I really need some help with a couple questions for this test review if anyone could help I'd greatly appreciate it.

"Evaluate the following indefinite integral by using the given substitution to reduce the integral to standard form."

(integral) 7(7x+21)^9 dx = .....?

Can someone show how to do this in logical steps please

This is a standard u-substitution problem. Do you know how to do those types of integrals? What have you tried so far?

 

[jiblition]

I guess my issue is why is my answer wrong, I have u as 7x+21 and du as the rest, so 7 dx, which then becomes (u)^9 du -> (u)^10/10+C --->
(7x+21)10/10 +C is what i have..but it was marked wrong in the mathlab and I can't figure out why. Can't really simplify that further either as far as I know....

 

[Deleted member 4993]

I guess my issue is why is my answer wrong, I have u as 7x+21 and du as the rest, so 7 dx, which then becomes (u)^9 du -> (u)^10/10+C --->
(7x+21)10/10 +C is what i have..but it was marked wrong in the mathlab and I can't figure out why. Can't really simplify that further either as far as I know....

Did you put that or

(7x+21)^10/10 + C

as your answer?

 

[jiblition]

I put (7x+21)^10/10+C as my answer[sorry for typo], but apparently I'm not allowed to use the fraction in the answer in the math lab? So if i multiply it out wouldn't i have *10/1 not 1/10(7x+21)^10+C as what they list?

 

[stapel]

I put (7x+21)^10/10+C as my answer[sorry for typo], but apparently I'm not allowed to use the fraction in the answer in the math lab? So if i multiply it out wouldn't i have *10/1 not 1/10(7x+21)^10+C as what they list?

You've made reference to a "given" substitution, but haven't provided it (that I can tell; you mentioned something you'd tried, but didn't specify that it was what they'd told you to use). You've mentioned making repeated attempts, but haven't provided a clear listing of all of your steps for any of them. You seem now to be making reference to answer options for what sounds like a multiple-choice question, and are asking us about the formatting requirements.

We can help you with the math, but you'll need to reply with ALL of the information: the exact question, the complete instructions (including the required substitution), all of your steps from at least one of your attempts, and the various options from which you are expected to choose. But we can't do the formatting stuff for you, since we aren't sitting in front of whatever console you're viewing. You'll need to consult with your instructor or with tech support for the specifics there.

So please do reply with a clear statement of all the necessary information. Thank you!

 

[jiblition]

There are no answer options to a multiple choice or anything like that. It's a review for class. I have the answer. I'm solving via substitution. I was trying to understand why my answer was wrong / how to get to that answer I listed. I did provide the steps. I will list them again.

The problem is (integral) 7(7x+21)^9 dx.
I listed u as 7x+21.
I listed du as 7 dx.
I then did (u)^9 du.
I then did (u)^10/10+C.
I then did (7x+21)^10/10+C as my answer.
Which was marked wrong in the online portal for simplification errors. Which I do not understand.
They list the answer as 1/10(7x+21)^10 +C, but if they multiplied the /10 from the denominator out, wouldn't that alter the rest?

 

[srmichael]

There are no answer options to a multiple choice or anything like that. It's a review for class. I have the answer. I'm solving via substitution. I was trying to understand why my answer was wrong / how to get to that answer I listed. I did provide the steps. I will list them again.

The problem is (integral) 7(7x+21)^9 dx.
I listed u as 7x+21.
I listed du as 7 dx.
I then did (u)^9 du.
I then did (u)^10/10+C.
I then did (7x+21)^10/10+C as my answer.
Which was marked wrong in the online portal for simplification errors. Which I do not understand.
They list the answer as 1/10(7x+21)^10 +C, but if they multiplied the /10 from the denominator out, wouldn't that alter the rest?

As long as you typed in your answer as either $\displaystyle \dfrac{(7x+21)^{10}}{10}+C$ or $\displaystyle \dfrac{1}{10}(7x+21)^{10}+C$ you should have been marked correct as they are equivalent.

 

[fcabanski]

This is what "they" did. Instead of writing 3/10 they wrote 1/10 * 3. The answers are equivalent, as the last poster mentioned.

Talk to the instructor to clarify. Or call the company that operates the online course and testing portal. If they mark your answer as incorrect, they are in error.

 

[Cheezees]

Parentheses

I think you were supposed to type ((7x+21)^10)/10 + C. The extra pair of parentheses may have been needed. Some computer programs are finicky that way. Hope this helps!