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(3xy^2-y^3)dx-(2x^2y-xy^2)dy=0 |
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Answer» Now, (3xy² - y³) DX - (2x²y - xy²) DY = 0 ⇒ dy/dx = (3xy² - y³)/(2x²y - xy²) ...(i) LET us take, y = vx Then, dy/dx = v + X (dv/dx) From (i), we get v + x (dv/dx) = (3x v²x² - v³x³)/(2x² vx - x v²x²) ⇒ v + x (dv/dx) = (3v² - v³)/(2v - v²) ⇒ x (dv/dx) = (3v - v²)/(2 - v) - v ⇒ x (dv/dx) = (3v - v² - 2v + v²)/(2 - v) ⇒ x (dv/dx) = v/(2 - v) ⇒ {(2 - v)/v} dv = (dx)/x ⇒ 2 (dv)/v - dv = (dx)/x ∴ integrating we get 2 ∫ (dv)/v - ∫ dv = ∫ (dx)/x ⇒ 2 logv - v = logx + c, where c is intergral constant ⇒ 2 log (y/x) - (y/x) = logx + c [ ∵ y = vx ] ⇒ 2 logy - 2 logx - (y/x) = logx + c ⇒ 2 logy - 3 logx = (y/x) + c, which is the required primitive # |
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