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patbatE21
 3 years ago
Integrate (9  x^2  x 1)dy from x = 1 to x = 2
patbatE21
 3 years ago
Integrate (9  x^2  x 1)dy from x = 1 to x = 2

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TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1what problem exactly do you have with this integral?

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1well the I'm actually trying to sketch a region enclosed by given curves

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1but i think there is something wrong with my integration...so far I have 9y 1/3y^3 1/2y^2  y

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1first off I assume you mean (9  x^2  x 1)dx

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1so then you answer is correct if you replace y's with x's

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1the actual question is " Sketch the region enclosed by the given curves. Decide whether to integrate with respect to x or y. Draw a typical approximating rectangle and label its height and width. Then find the area of the region

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1y = x + 1, y = 9  x^2, x = 1, x = 2

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1I am just having issues finding the area

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1let's just do the integral first, yeah?

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1I know that I will have to take the integral [f(y) g(y)] from c to d

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1It's f(x)g(x) I think you are having a problem keeping track of variables, remember y=f(x), so f(y) is something different and undefined here.

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1I believe that is my problem, understood

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1so your integral is\[\int\limits_{1}^{2}9x^2x1dx\]

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1your answer is right replaced with x's\[9x{1\over3}x^3{1\over2}x^2x\]evaluated from 1 to 2, what do you get?

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1Sorry 19.5 Just the evaluation, right? As you see I hate that too, here's a site, if you don't already know it that's good for that. http://www.wolframalpha.com/ and here's your particular problem http://www.wolframalpha.com/input/?i=Integrate+%289++x%5E2++x+1%29dx+from+1+to+2

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1wait a minute this is all wrong! I should have noticed sooner!

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1No its correct I just submitted it online and it is marked correct

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1did you mean it as you typed it? 9  x^2  x 1 are you mot missing an x? because 91=8 so the integration we di is wrong

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1I see what you mean, but how is it still correct

TuringTest
 3 years ago
Best ResponseYou've already chosen the best response.1Okay it's not ALL wrong, but the way wee did it is silly, it may be right, but we failed to notice that \[9  x^2  x 1=8x^2x\] So we integrated an extra term. It is important to see shortcuts like that, so at least look for those in the future :)

patbatE21
 3 years ago
Best ResponseYou've already chosen the best response.1Ok, the ahhah moments in math...such a wonderful subject
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