Respuesta :

mathmate

Answer:

Step-by-step explanation:

Interesting problem.

At 6<x<8,

f(x) = x-7

at 5<x<8

g(x) = (15-x)/2

=>

y(x)

= f(x)*g(x)

= (x-7)(15-x)/2

= (x^2+22x-105)/2

differentiate y(x) with respect to x,

y'(x) = -x+11

at x = 7,

y'(7) = -(7) + 11 = 4

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