Differential Equations: $(x - 2y - 1) dy = (2x - 4y - 5) dx$
Coefficient Linear in Two Variables? Help please.
(x-2y-1)dy=(2x-4y-5)dx
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Coefficient Linear in Two Variables? Help please.
(x-2y-1)dy=(2x-4y-5)dx
By inspection, we can see
By inspection, we can see that both sides of the equation contains x - 2y.
$(x - 2y - 1)\,dy = (2x - 4y - 5)\,dx$
z = x - 2y
dz = dx - 2dy
dx = dz + 2dy
$(z - 1)\,dy = (2z - 5)(dz + 2dy)$
$(z - 1)\,dy = (2z - 5)\,dz + 2(2z - 5)\,dy$
$(z - 1)\,dy - 2(2z - 5)\,dy = (2z - 5)\,dz$
$(z - 1 - 4z + 10)\,dy = (2z - 5)\,dz$
$(9 - 3z)\,dy = (2z - 5)\,dz$
$dy = \dfrac{(2z - 5)\,dz}{9 - 3z}$
$dy = \left( -\dfrac{2}{3} + \dfrac{1}{9 - 3z} \right) \, dz$
$y + c = -\frac{2}{3}z - \frac{1}{3}\ln (9 - 3z)$
$y + c = -\frac{2}{3}(x - 2y) - \frac{1}{3}\ln \Big[ 9 - 3(x - 2y) \Big]$
$-\frac{1}{3}y + c = -\frac{2}{3}x - \frac{1}{3}\ln (9 - 3x + 6y)$
$y + c = 2x + \ln (9 - 3x + 6y)$ answer
Can we factor out (9-3x+6y)
In reply to By inspection, we can see by Jhun Vert
Can we factor out (9-3x+6y) to make it 3ln(3-x+2y) is that valid?
Note that ln (xy) = ln (x) +
In reply to By inspection, we can see by Jhun Vert
Note that ln (xy) = ln (x) + ln (y), the same as
ln (ax) = ln (a) + ln (x) ≠ a ln (x).
For
ln (9-3x+6y) = ln [3(3-x+2y)] = ln (3) + ln (3-x+2y)
Oh. Thank you, sir.
In reply to Note that ln (xy) = ln (x) + by Jhun Vert
Oh. Thank you, sir.
how did you do it? dy=(2z−5
In reply to By inspection, we can see by Jhun Vert
how did you do it? dy=(2z−5)dz9−3z
dy=(2z−5)dz9−3z
long division
In reply to how did you do it? dy=(2z−5 by Ale Mendez
long division
Parallel or intersecting
Parallel or intersecting lines?