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ÂÏÐÀÂÈ<br />
Ðîçâ’ÿçàòè ð³âíÿííÿ:<br />
11.1. ( x + xy) dx + ( y + xy) dy = 0;<br />
2 2<br />
11.2. yy ( − 1) dx+ xx ( − 1) dy=<br />
0;<br />
2 2<br />
11.3. xy ( − 1) dx+ yx ( − 1) dy=<br />
0;<br />
2 2<br />
11.4. sec x⋅ tg ydx + sec y⋅ tg xdy = 0;<br />
2 1<br />
Âêàç³âêà. sec x =<br />
2 ;<br />
cos x<br />
2 2<br />
11.5. x 1+ y dx + y 1+ x dy = 0;<br />
11.6 − ycos xdx + sin xdy = 0;<br />
11.7. yln ydx + xdy = 0;<br />
y<br />
x<br />
11.8. xe dx + ye dy = 0;<br />
y + N dx + x + N dy = 0;<br />
2 2 2 2<br />
11.9. ( ) ( )<br />
N<br />
N<br />
11.10. x ydy + y xdx = 0;<br />
x 1+ Ny dx + y 1+ Nx = 0;<br />
11.11. ( ) ( )<br />
2 2 2 2<br />
11.12. x N + y dx + y N + x dy = 0;<br />
2 2 2 2<br />
11.13. N − x dx + N − y dy = 0;<br />
2 2 2 2<br />
11.14. N − x dy + N − y dx = 0.<br />
ßê ³ ðàí³øå, ïàðàìåòð N îçíà÷ຠ÷èñëî äàòè íàðîäæåííÿ<br />
÷èòà÷à, ÿêèé áóäå âèêîíóâàòè âïðàâè 11.9–11.14.<br />
11.4.2.2. Îäíîð³äí³ ð³âíÿííÿ<br />
Äèôåðåíö³àëüíå ð³âíÿííÿ ïåðøîãî ïîðÿäêó íàçèâàºòüñÿ<br />
îäíîð³äíèì, ÿêùî éîãî ìîæíà çîáðàçèòè ó âèãëÿä³:<br />
⎛y<br />
⎞<br />
y′ =ϕ ⎜<br />
x ⎟<br />
⎝ ⎠ , (11.4.18)<br />
äå ïðàâà ÷àñòèíà º ôóíêö³ºþ ò³ëüêè â³ä â³äíîøåííÿ çì³ííèõ.<br />
Äèôåðåíö³àëüíå ð³âíÿííÿ (11.4.18) çâîäèòüñÿ äî ð³âíÿííÿ<br />
ç â³äîêðåìëþâàíèìè çì³ííèìè øëÿõîì ï³äñòàíîâêè<br />
y<br />
z = ( y = zx)<br />
. ijéñíî:<br />
x<br />
dy dz<br />
= z+ x .<br />
dx dx<br />
ϳäñòàâëÿþ÷è öåé âèðàç ïîõ³äíî¿ ó ð³âíÿííÿ (11.4.18),<br />
îòðèìàºìî:<br />
dz<br />
z+ x = ϕ () z . (11.4.19)<br />
dx<br />
гâíÿííÿ (11.4.19) — ð³âíÿííÿ ç â³äîêðåìëþâàíèìè<br />
çì³ííèìè, ÿêå ðîçâ’ÿçóºòüñÿ ìåòîäîì, çàçíà÷åíèì âèùå.<br />
ϳäñòàâëÿþ÷è ï³ñëÿ ³íòåãðóâàííÿ ð³âíÿííÿ (11.4.19) çàì³ñòü<br />
z â³äíîøåííÿ y , îòðèìàºìî çàãàëüíèé ³íòåãðàë ð³âíÿííÿ<br />
(11.4.18).<br />
x<br />
Ïðèêëàä 11.4.5. Ðîçâ’ÿçàòè ð³âíÿííÿ<br />
2 2<br />
2xyy′ = x + y . (11.4.20)<br />
Ð î ç â ’ ÿ ç à í í ÿ. Çàïèøåìî ð³âíÿííÿ (11.4.20) ó âèãëÿä³:<br />
2 2<br />
dy x + y<br />
= , àáî<br />
dx 2xy<br />
( y x)<br />
( )<br />
dy 1 + /<br />
= .<br />
dx 2 y / x<br />
Çä³éñíþþ÷è ï³äñòàíîâêó y = xz, îäåðæóºìî<br />
2 2<br />
dz 1+ z dz 1−z<br />
z + x = àáî x = .<br />
dx 2z dx 2z<br />
 îòðèìàíîìó ð³âíÿíí³ çì³íí³ â³äîêðåìëþþòüñÿ:<br />
dx 2zdz<br />
=<br />
2 .<br />
x 1 − z<br />
2<br />
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