y = x^2 - 28x + 96lnx - 3
y ' = (x^2 - 28x + 96lnx - 3) ' = (x^2)' - 28(x)' + 96*(lnx)' - (3)' =
= 2x^2 - 28 + 96/x
y' = 0
2x - 28 + 96/x = 0
2x^2 - 28x + 96 = 0 /:2
x^2 - 14x + 48 = 0
(x - 6)(x - 8 ) = 0
x = 6
x = 8
+ - +
------------ (6) ----------- (8) ------------> x
x = 6 max
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