AP EAMCET201920 Apr 2019Morning ShiftMathematicsDifferential EquationsActual
If (c ) is a parameter, then the differential equation of the family of curves (x^2=c(y+c)^2 ) is
Options
- A(x ( d y d x )^3+y ( d y d x )^2-1=0 )
- B(x ( d y d x )^3-y ( d y d x )^2+1=0 )
- C(x ( d y d x )^3+y ( d y d x )^2+1=0 )
- D(x ( d y d x )^3-y ( d y d x )^2-1=0 )
Correct answer
D. (x ( d y d x )^3-y ( d y d x )^2-1=0 )
Step-by-step solution
Given equation of the family of curves ( aligned & x^2=c(y+c)^2 & x= c (y+c) (i) aligned ) [on taking square root both sides] Now, differentiate both sides w.r.t. (x ), we get ( aligned I & = c d y d x c & = d x d y (ii) aligned ) From Eqs. (i) and (ii) on eliminating ' (c ) ', we get ( aligned & x= ( d x d y ) [y+ ( d x d y )^2 ] & x ( d y d x )^3=y ( d y d x )^2+1 & x ( d y d x )^3-y ( d y d x )^2-1=0 aligned ) Hence, option (4) is correct.