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Question
The relation between the number of words y a person learns in x hours is given by y = `sqrt(x), 0 ≤ x ≤ 9`. What is the approximate number of words learned when x changes from 4 to 4.1 hours?
Solution
y = `52sqrt(y)`
dy = `52 xx 1/2 xx x^((-1)/2) "d"x`
x = 4
dx = 0.1
`26/sqrt(4) xx 0.1` = 13 × 0.1
= 1.3
≅ 1 word
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