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Calculus / English

Mean Value Theorem

The Organic Chemistry Tutor · YouTube · 19:39

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The explanation, unpacked.

Reviewed learning material · Video analysis · English
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Apply the mean value theorem carefully, distinguishing endpoint behavior from interior differentiability.

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Chapters

0:00Check both hypotheses6:00Solve for the matching slope9:00Endpoint versus interior corner

Learning script

Generated from the video's visuals and explanation; not verbatim speech.

For a<ba<b, continuity on [a,b] and differentiability on (a,b) guarantee an interior point where the tangent slope equals the secant slope.

For f(x)=xf(x)=x²−4x+14x+1 on [1,5], the secant slope is (6−(−2)6-(-2))/4=2. Solving 2c−4=22c-4=2 gives c=3c=3, inside the interval.

The cusp of x(2/3)x^(2/3) at the endpoint 0 does not violate differentiability on (0,1). By contrast |4x−54x-5| has a corner at 5/45/4 inside (0,2), so the theorem does not apply there.

Knowledge cards

01

Check both hypotheses

For a<ba<b, continuity on [a,b] and differentiability on (a,b) guarantee an interior point where the tangent slope equals the secant slope.

02

Solve for the matching slope

For f(x)=xf(x)=x²−4x+14x+1 on [1,5], the secant slope is (6−(−2)6-(-2))/4=2. Solving 2c−4=22c-4=2 gives c=3c=3, inside the interval.

03

Endpoint versus interior corner

The cusp of x(2/3)x^(2/3) at the endpoint 0 does not violate differentiability on (0,1). By contrast |4x−54x-5| has a corner at 5/45/4 inside (0,2), so the theorem does not apply there.

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  • Mean value theorem ExplanationAt 0:00
    Why this connection?

    For a<ba<b, continuity on [a,b] and differentiability on (a,b) guarantee an interior point where the tangent slope equals the secant slope. For f(x)=xf(x)=x²−4x+14x+1 on [1,5], the secant slope is (6−(−2)6-(-2))/4=2. Solving 2c−4=22c-4=2 gives c=3c=3, inside the interval. The cusp of x(2/3)x^(2/3) at the endpoint 0 does not violate differentiability on (0,1). By contrast |4x−54x-5| has a corner at 5/45/4 inside (0,2), so the theorem does not apply there.