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Mth 174

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chapter 7 book problems

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7.8.13 integral from 5 to 8 of 6/(sqrt (t-5)) dt

7.8.15 integral from -1 to 5 of 1/[(t+1^2)]

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In number 13, p < 1 so why does this converge?

In number 15, p > 1 so why does this not converge?

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You can find the antiderivative for #13; just let w = t - 5, integrate 6 / sqrt(w), etc..

#15 is probably the integral of (t + 1)^2. This is undefined at t = -1, so using tau to stand for the lower limit of the integral, we have to find the limit as tau -> -1 of the integral from tau to 5.

An antiderivative is -1 / (t + 1). Evaluated at limits tau and 5 we get

-1 / (5 + 1) - (-1 / (tau + 1) )

= -1/6 + 1 / (tau + 1).

As tau -> -1, tau + 1 approaches zero and 1 / (tau + 1) approaches infinity.

Thus the integral diverges.

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