Oblicz całkę:
f 2x2 + 2x + 1 ./ x2(x + 1)
Rozwiązanie:
Rozkładam na sumę ułamków prostych.
2x2 + 2x+l _ A B_ C
X2 [x + 1) X X2 X + 1
2x2 + 2x + 1 Ax(x + 1) B(x + 1) Cx2
x2(x + 1) x2(x + 1) x2(x + 1) x2(x + 1)
2x2 + 2x + 1 _ Ax(x + 1) + B(x + 1) + Cx2 x2(x + 1) x2(x + 1)
2x2 + 2x + 1 = Ax(x + 1) + B(x + 1) + Cx2
2x2 + 2x + 1 = Ax2 + Ax + Bx + B + Cx2
2x2 + 2x+\ = (A + C)x2 + {A+ B)x + B
{A + C — 2 A + B = 2
B= 1
{A+C=2 A+ 1=2 B= 1
/
2x2 + 2x + 1
x2(x + 1)
*.fa+4
J \x x‘
2 x + 1
dx
= / —dx + / ~^rdx + [ —-—dx = J x J x2 J x + 1
— ln |x| + C\---h C*2 + ln \x + 1| + C3
x
= ln |a;| + ln |a; + 1|---1- C
Na podstawie wzorów: logn x + log0 y = log0 xy i |a:| • |y| = \x ■ y\
= ln |a;(x + 1)|---YC
IH
Odp.
+ 2x + 1 .1/ .. i 1 „
.,7-7—dx = ln a:(x +1)---1-C
a:2 (a: + 1) x