f(x) x 1 (maximum), f(x 1 + ∆x) < f(x 1 ) ∆x ( ), , .. f(x) x 1 , , x 1.
3
f(x) (minimum) x=x 2, f(x 2 +∆x) > f(x 2 ) ∆x , , .
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1. , , x, .
2. , : , , , , , .
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[ , b ] .
.
3 ( )
y= f(x) x=x 1 , , .. f'(x) =0.
. , x=x1 . ∆x (∆x≠0) f(x1+ ∆x) < f(x1), .. f(x1+ ∆x) - f(x1) < 0.
∆ x, :
> 0, ∆ x <0,
<0, ∆ x <0.