-u’=-(x+a)-2, u’’=2(x+a)-3, u’’’=-2-3(x+a)~3=-6(x+a)~4.
Matematik induksiya metodi bilan
u(n)=(-1)nn!(x+a)-n~1 (8)
Shunday qilib, (8.7) va (8.8) tengliklardan foydalanib quyidagi
y
(x - 3 )n (x - 2)
n
J
in=-7-(-1)n -n!(x-2)~n+9-(-1)n -n!(x-3)~n=(-1)n n! natijaga erishamiz
.Leybnits formulasi.
Agar u(x) va v(x) funksiyalar n-tartibli hosilalarga ega bo‘lsa, u holda bu ikki funksiya ko‘paytmasining n -tartibli hosilasi uchun
(uv )(n) = u(n)v + Cn' u(n-1)v'+C2nu(n-2 )v''+... + Cknu(n - k)v(k) +... + + Cnn-1u'v(n-1) + uv(n) (9) k n(n -1 )...(n - k +1)
formula o‘rinli bo‘ladi. Bunda C
n
k!
Isboti. Matematik induksiya usulini qo‘llaymiz. Ma’lumki,
(uv)’=u’v+uv’. Bu esa n=1 bo‘lganda (9) formulaning to‘g‘riligini ko‘rsatadi. Shuning uchun (9) formulani ixtiyoriy n uchun o‘rinli deb olib, uning n+1 uchun ham to‘g‘riligini ko‘rsatamiz. (9) ni differensiyalaymiz:
(uv)n +1 = u(n +1)v + u(n)v'+C'nu(n)v'+Cn' u(n-1)v''+Clu(n-1)v''+C^u(n - 2 )v'''+ +... + Cknu(n-k+1}v(k) + Cknu(n-k)v(k +1) +... + Cnn -1u"v(n-1) + Cnn -1u’v(n) +
+ u'v(n) + uv(n+ 1) (10)
Ushbu
1 + Cn' = 1 + n = Cn+1, Cn' = n + ^ ^
rk-1 . nk _ n(n - 1)...(n + 2 - k) n(n - 1 )...(n - k +1) _ n n = (k -1)! k! ~
_(n +1 )n...(n +1 - (k -1)) k k! ^ tengliklardan foydalanib, (10) ni quyidagicha yozamiz:
(uv )n+1 = u(n+1 )v + Cln+lu(n)v'+C1n+lu(n-1 )v''+...+Ck+1u(in+1-k\(k) +... + uv(n+1)
Demak, (9) formula n+1 uchun ham o‘rinli ekan. Isbot etilgan (9) formula Leybnits formulasi deb ataladi
.Leybnits formulasi tatbiqlari.
Misol. y=x3ex ning 20-tartibli hosilasi topilsin.
Yechish. u=ex va v=x3 deb olsak, Leybnits formulasiga ko‘ra
/20) = x3(ex}(20) + C120(x3 )'(ex )(19) + C20(x3 }"(ex}(18) + C320(x3 }'"(ex}(11) +
+ C4(x3)(4)(ex/6 +...+ (x3)(20)ex bo‘ladi. (x3)’=3x2, (x3)’’=6x, (x3)’’’=6, (x3)(4)=0
tengliklarni va y=x funksiyaning hamma keyingi hosilalarining 0 ga tengligini, shuningdek Vn uchun (ex)(n=ex ekanligini e’tiborga olsak,
y(20) = ex (x3 + 3C^0x2 + 6C20x + 6C20 ) tenglik hosil bo‘ladi.
Endi koeffitsientlarni hisoblaymiz:
CL = 20, C220 =^=190, c30 = ^ ^=1140
Demak,
y( 20) = ex (x3 + 60x2 +1140x + 6840).
MUNDARIJA.
d 2 y d 2 f(x) 5
dx dx 6
d3 y d3 f(x ) 7
dx dx 7
dny dnf(x) 8
dx n dx n 9
1 15
^ 1 Л(п) 1 (-1 )n ■ n! = (-1)(-2)... (-n)x -1-n = ( • (2) 16
v x J xn+1 16
y(ny = (У) 18
xn 18
v x J 18
y' = cos x = sin( x + ^) 19
y” = (cosx)' = - sinx = sin(x + 2 ■—), 7Г y''' = (- sinx)' = - cosx = sin( x + 3 ■—), y(IV)) = (- cos x)' = sinx = sin( x + 4 7) 20
(cosx)(n = cos( x + n^) (5) 23
(cosx)(115 = cos( x +115 ~) = cos( x + = sinx. 25
2.Ikkinchi tartibli hosilaning mexanik ma’nosi. 25
2 x + 3 34
x — 5x + 6 35
2x + 3 A B 36
(x — 2)(x — 3) x — 2 x — 3 37
A + B = 2, [— 3 A — 2 B = 3 38
1 1 38
x — 2 x — 3 39
1 , 39
x + a 40
(uv )(n) = u(n)v + Cn' u(n-1)v'+C2nu(n-2 )v''+... + Cknu(n - k)v(k) +... + + Cnn-1u'v(n-1) + uv(n) (9) k n(n -1 )...(n - k +1) 3
k! 4
(uv)n +1 = u(n +1)v + u(n)v'+C'nu(n)v'+Cn' u(n-1)v''+Clu(n-1)v''+C^u(n - 2 )v'''+ +... + Cknu(n-k+1}v(k) + Cknu(n-k)v(k +1) +... + Cnn -1u"v(n-1) + Cnn -1u’v(n) + 5
CL = 20, C220 =^=190, c30 = ^ ^=1140 11
Azlarov. T., Mansurov. X., Matematik analiz. T.: «O‘zbekiston». 1 t: 2005, 2 t . 1995
Fixtengols G. M. „Kurs differensialnogo i integralnogo ischeleniya“ M.: 1970.
Sa’dullayev A. va boshqalar. Matematik analiz kursi misol va masalalar to'plami. T., «O‘zbekiston». 1-q. 1993., 2-q. 1995.
Demidovich B. P. “Sbornik zadach i uprajneni po matematicheskomu analizu” T.: 1972.
Ilin V. A., Poznyak E. G. “Maematik analiz asoslari” I qism, T.: 1981.
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