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How do I work this Calculus problem?!?
So this is a free response question from the 1988 AB Calculus exam... It's question number 5.
Let R be the region in the 1st quadrant under the graph y = (x)/(x^2+2) for 0<=x<=(6^.5).
A.) Find the area of R
B.) If the line x=k divides R into two regions of equal area, what is the value of k?
C.) What is the average value of the function on its interval.
C. is my main problem. I'm pretty sure I got A and B. But help on any of them for assurance would be great thanks!
2 Answers
- King CalcLv 51 decade agoFavorite Answer
Hi Jared.
A) Find the area of "R".
This is going to require integrals. You need to take the integral from "0" to "√6" of the equation given.
∫ [x / (x² + 2)]dx
Take the antiderivative F(x) of the integral.
F(x) = ln(x² + 2) / 2
Take the sum of the antiderivative on the interval given.
[ln(√6² + 2) / 2] - [ln(0² + 2) / 2]
Simplify.
[ln(8) / 2] - [ln(2) / 2]
Simplify further.
[ln(2³) / 2] - [ln(2) / 2]
Simplify further.
[3ln(2) / 2] - [ln(2) / 2]
Simplify further.
2ln(2) / 2
Simplify further.
ln(2) <= FINAL ANSWER
_______________
Unfortunately we haven't been taught how to do this in class yet, so I can't help you with this one.
_______________
C) What is the average value of the function on its interval?
For this, you need to use the Mean Value Theorem (for integrals). This theorem states the following:
If f is integrable on [a, b], then its mean value on that interval is
[1 / (b - a)] × [the integral from "a" to "b" of f(x)].
So basically just follow the equation that they give you and substitute in your values. We already found the integral of the function, so really you are just multiplying it by a fraction.
[1 / (√6 - 0)] × ln(2)
Simplify.
1 / (√6) × ln(2)
Simplify further.
ln(2) / (√6)
Rationalize the denominator.
(√6)ln(2) / 6 <= FINAL ANSWER
I hope this helped. (:
- ?Lv 45 years ago
f (x) = x^3 - 12x + a million . . . the first by-product set to 0 unearths turning or table certain factors f ' (x) = 3x^2 - 12 3x^2 - 12 = 0 3 * (x + 2) * (x - 2) = 0 x = 2 ... x = - 2 . . . the second one by-product evaluated at x = 2 and -2 determines if those factors are min, max, or neither. f ' ' (x) = 6x f ' ' (2) = 6*2 = 12 <== useful fee shows x=2 is an section minimum f ' ' (-2) = 6*(-2) = -12 <== damaging fee shows x=-2 is an section optimal a.) x = - 2 is a optimal, and x=2 is a minimum ... so x = - infinity to -2 is increasing x = -2 to +2 is lowering x = +2 to + infinity is increasing b.) f (-2) = (-2)^3 - 12*(-2) + a million = 17 f (2) = (2)^3 - 12*(2) + a million = - 15 c.) . . . the second one by-product set to 0 unearths inflection factors, or the position concavity alterations 6x = 0 x = 0 <=== inflection element x = - 2 is a optimal, so must be concave down concavity alterations on the inflection element(s) ... so x = - infinity to 0 is concave down x = 0 to + infinity is concave up