8. , , , .
: , , , .
9. y = f(x) () X, x1,x2Î X
f (l1 x 1+l2 x 2)£ l1 f (x 1)+ l2 f (x 2) (f (l1 x 1+l2 x 2)³ l1 f (x 1)+ l2 f (x 2)),
l1³ 0,l2³ 0, l1+l2 = 1.
, , . 25.
9. () X , ().
, f'(x) () X, () (.26). ().
().
10 ( ). () X, () .
. f''(x)>0, xÎ X, f'(x) X X. , f''(x)<0.
: () X, f''(x)³ 0, xÎ X ( f''(x)£ 0) xÎ X. , y = x4 , y'' = 12x2 x = 0.
10 ( ). , , .
, - . .
11 ( ). f''(x) x 0 , .. f''(x 0 ) = 0.
12 ( ). x 0, f''(x 0 ) = 0 , x 0 .
, x1 , , x2 , . x0 - . (. 27).
, .
13. y = x4+x3-18x2+24x -12.
.
y' = 4 x 3+3 x 2-36 x+ 24, y'' = 12 x 2+6 x- 36.
y'' = 0 x1 = -2, x2 = 3/2. , y''>0 (-¥,-2), (3/2,¥) ; y''<0 (-2,3/2) . x1 = -2 x2 = 3/2 , (-2,-124) (3/2,-129/16) .
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11 ( ). x = a y = f(x),
lim x a+ 0 f (x) lim x a- 0 f (x)
+¥ -¥.
14. y = 1/(x-2) x = 2, limx 2+01/(x-2) = +¥, limx 2-01/(x-2) = -¥ (.28).
12 ( ). , y = kx+b y = f(x) x +¥, f(x)
f (x) = kx+b+ a (x),
limx +¥a (x) = 0.
13 ( ). y = f(x) x +¥ y = kx+b, ,
lim x +¥ f (x) /x = k, lim x +¥(f (x) -kx) = b.
.
1. . y = f(x) x +¥ y = kx+b, f(x)
f (x) = kx+b+ a(x),
lim x +¥ f (x) /x = (kx+b+ a(x)) /x = k,
lim x +¥(f (x) -kx) = lim x +¥(b+ a(x)) = b.
2. . , . f(x)-kx-b x +¥. f(x)-kx-b = a(x) , f(x) .
. 13 x -¥.
. k=0 , .
15. :
y = 5 x/ (x- 3).
. x = 3,
lim x 3 05 x/ (x- 3) = ¥.
:
k = lim x ¥ y/x = lim x ¥5 x/x (x- 3) = 0. b = lim x ¥(y-kx) =lim x ¥5 x/ (x- 3) = 5.
, x = 3 y = 5.