Gregg K. answered • 12/13/16

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#mathtutor AP Calculus & AP Statistics Teacher / College Teacher

x^2 + y^2 =100

2x(x') + 2y(y') = 0

we are solving for y'

y ' = -x(x ')/y

We are given x ' = .6

We are given x = 8

We need to find y

we have x^2 + y^2 = 100

Therefore when x = 8, y = 6

So, y ' = -8(.6)/6

y ' = -.8

sliding down at .8 m/s

Gregg K.

tutor

Because I said sliding down , the word down would indicate the negative

It is moving down at .8m/s

Your question asks how fast is the ladder slidding DOWN the wall

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12/13/16

Gregg K.

tutor

the height of the top of the ladder (y) is decreasing with the ground as the reference point. That is why y ' is negative

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12/13/16

Gregg K.

tutor

If you simply asked what the rate of the top of the ladder was I would have said -.8 m/s

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12/13/16

Alex C.

12/13/16