MA102: First Order ODEs
Tutorial 1
1. Classify the following Differential equations: Linear/ Non-linear/ Ordinary/ Par-
tial, etc. and specify the order.
(a) y ′′ + 3y ′ + 20y = ex ,
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(b) 1 + y 3 = x2 ,
(c) y ′′ + y 2 = cos(x),
(d) y ′ + xy = cos(y ′ ),
(e) (xy ′ )′ = xy,
(f) ux + uy = 0,
(g) uxx + uyy = ut .
2. Consider the differential equations y ′ = θy; x > 0; where θ is a constant. Show
that
(a) if ϕ(x) is any solution and ψ(x) = ϕ(x)e−θx , then ψ(x) is a constant;
(b) if θ < 0, then every solution tends to zero as x → ∞.
3. Solve the following Differential equations:
(a) x2 y ′ = 3(x2 + y 2 ) arctan xy + xy,
(b) y ′ = sin2 (x − y + 1).
ax+by+c
4. (a) Reduce the differential equation y ′ = f dx+ey+f
, ae − bd ̸= 0 to a separable
variable form. What happens if ae = bd ?
(b) Hence, find the general solution of the following differential equations:
i. (x + 2y + 1) − (2x + y − 1)y ′ = 0,
(8x−2y+1)2
ii. y ′ = (4x−y−1)2
.
5. By making a substitution v = xyn or y = vxn and choosing suitable n, show that
the following differential equations can be transformed into separable variables,
and hence solve them:
1−xy 2
(a) y ′ = 2x2 y
,
2+3xy 2
(b) y ′ = 4x2 y
.
6. Show that the following equations are exact and, hence, find their general solution:
(a) (cos(x) cos(y) − cot(x))dx − (sin(x) sin(y))dy = 0,
2 2
(b) 2x(y + 3x − ye−x )dx + (x2 + 3y 2 + e−x )dy = 0.
(c) (x + 2y − 3)dy − (2x − y + 1)dx = 0.
(d) y(sin 2x)dx − (1 + y 2 + cos2 x)dy = 0
7. Show that 2 sin(y 2 )dx + xy cos(y 2 )dy = 0 admits an integrating factor which is a
function of x only. Also, solve the differential equation.
8. A. Consider homogeneous equation M (x, y)dx + N (x, y)dy = 0. If Mx + Ny ̸= 0,
1
then Mx +N y
is an integrating factor of the differential equation. Using this,
solve the following equation:
(4y 2 + 3xy)dx − (3xy + 2x2 )dy = 0.
B. Further, multiply with xα y β and find α and β such that the corresponding
equation becomes exact. Hence, find the solution. Compare both solutions!
9. Reduce the following differential equations into linear form and solve:
y3
(a) y 2 y ′ + x
= sin(x),
(b) y ′ sin(y) + x cos(y) = x,
(c) y ′ = y(xy 3 − 1),
(d) (ey − 2xy)y ′ = y 2 ,
(e) y − xy ′ = y ′ y 2 ey .
10. Use Picard’s method of successive approximation to solve the following initial value
problems and compare these results with the exact solutions:
√
(a) y ′ = 2 x; y(0) = 1,
(b) y ′ + xy = x; y(0) = 0,
(c) y ′ = 2 y3 ; y(0) = 0.
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11. Find the differential equation corresponding to the following family of curves:
(a) xy 2 − 1 = cy,
(b) y = ax2 + be2x ,
(c) y = a sin(x) + b cos(x) + b.