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अवकल समीकरण `(x + y)dy + (x-y)dx = 0` को हल कीजिए |

Answer» `because " " (x+y) dy + (x -y) dx = 0`
`(x+y) dy = (y-x) dx`
`(dy)/(dx) = (y-x)/(x+Y)`
यह एक समघाती अवकल समीकरण है |
यदि `y = vx,` तब `" " (dy)/(dx) = v + x (dv)/(dx)`
`therefore " " v +x (dv)/(dx) = (vx -x)/(x+vx)`
`x(dv)/(dx) = (v-1)/(v+1) -v`
`= (v-1-v^(2)-v)/(v+1) = (-(v^(2) + 1))/(v+1)`
`therefore " " (v+1)/(v^(2) + 1) dv + (edv)/(x) =0`
दोनों पक्षों का समाकलन करने पर,
`f""(v)/(v^(2)+1)dv+f""(1)/(v^(2)+1)dv+f""(dv)/(x) =c`
`rArr (1)/(2)f""(2v)/(v^(2)+1)dv+f""(dv)/(v^(2)+1)+f""(dx)/(x) =c`
`rArr (1)/(2)log(v^(2)+1)+tan^(-1) + logx =c`
` rArr (1)/(2)log (v^(2) + 1) + log x + tan^(-1)v =c `
`rArr (log(v^(2)+1)+21logx)/(2) + tan^(-1) v =c `
`rArr (log(v^(2) + 1) + log x ^(2))/(2) + tan^(-1) v =c `
`rArr (1)/(2) log (v^(2) + 1)x^(2) + tan^(-1) v =c `
`rArr (1)/(2) log(y^(2) + x^(2)) + tan^(-1)""(y)/(x) =c`.


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