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Let y=2(x^2)+4x+3. Find the differential dy when x=4 and dx=0.3Find the differential dy...

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masterpiece56 | Student | (Level 1) Honors

Posted March 30, 2012 at 2:15 PM via web

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Let y=2(x^2)+4x+3.
Find the differential dy when x=4 and dx=0.3
Find the differential dy when x=4 and dx=0.6

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justaguide | College Teacher | (Level 2) Distinguished Educator

Posted March 31, 2012 at 12:03 AM (Answer #1)

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The function y=2(x^2)+4x+3

dy = (4x + 4) dx

For x = 4 and dx = 0.3, dy = 20*0.3 = 6

For x = 4 and dx = 0.6, dy = 20*0.6 = 12

The value of dy when x = 4 and dx = 0.3 is 6 and when x = 4 and dx = 0.6 dy = 12.

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sciencesolve | Teacher | (Level 3) Educator Emeritus

Posted March 31, 2012 at 1:43 AM (Answer #2)

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You need to differentiate the function y with respect to x such that:

`(dy)/(dx) = (2x^2+4x+3)' =gt (dy)/(dx) = 4x + 4`

You need to multiply by dx both sides such that:

`(dy) = (4x + 4)(dx) `

You need to evaluate dy at x=4 and dx = 0.3, hence you should substitute 4 for x and 0.3 for dx such that:

`(dy) = (4*4 + 4)(0.3) `

`(dy) = (20)(0.3) =gt (dy) = 6`

You need to evaluate `dy`  at x=4 and `dx = 0.6` , hence you should substitute 4 for x and 0.6 for dx such that:

`(dy) = (4*4 + 4)(0.6)`

`(dy) = (20)(0.6) =gt (dy) = 12`

Hence, evaluating dy under given conditions yields `(dy) = 6 ` at `x=4`  and `dx=0.3` ; `(dy) = 12`  at `x=4`  and `dx=0.6` .

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