The first order system of equations equivalent to

$x''+p(t)x'+q(t)x=0$

is

$\frac{dX}{dt} =A(t)X with \; X= {\begin{pmatrix} x_1\\x_2\end{pmatrix} },$and $\frac{dX}{dt}=\begin{pmatrix} x'_1\\x'_2 \end{pmatrix},$

where A(t) is the $2\times2 matrix$

(a)  $\begin{pmatrix} 1&0\\-p&-q \end{pmatrix}$   (b)$\begin{pmatrix}0&1\\-q&-p \end{pmatrix}$(c)$\begin{pmatrix} 0&1\\q&p \end{pmatrix}$   (d) $\begin{pmatrix}-p&-q \\1&0\end{pmatrix}$

The function f(x, y) = x|y|,(x, y) ∈ R × R with respect to the y variable

(a) satisfies a Lipschitz condition on the strip −1 ≤ x ≤ 1, −∞ < y < ∞.

(b) satisfies a Lipschitz condition on the strip −∞ < x < ∞, −1 ≤ y ≤ 1.

(c) does not satisfy a Lipschitz condition on −1 ≤ x ≤ 1, −1 ≤ y ≤ 1.

(d) does not satisfy a Lipschitz condition at any point on R × R.

According to the excavated evidence, the domestication of animal began in
(A) Lower Palaeolithic period
(B) Middle Palaeolithic period
(C) Upper Palaeolithic period
(D) Mesolithic period

The initial value problem $\frac{dy}{dx}=x^2+y^2,y(0)=0$, in the neighborhood of (0, 0) has

(a) no solution

(b) a singular solution

(c) a unique differential solution

(d) infinite number of solutions

The largest interval on which the solution of the initial value problem $\frac{dx}{dt}=x^3$ , x(0) = 1 is defined as

(a) $t>\frac{1}{2}$      (b) $t<\frac{1}{2}$       (c) $\frac{-1}{2}<t<\frac{1}{2}$           (d) −1 < t < 0

The initial value problem $2x\frac{dy}{dx}=3(2y-1),y(0)=\frac{1}{2}$ has

(a) a unique solution

(b) more than one, but only finitely many solutions

(c) infinitely many solutions

(d) no solution

The differential equation $y''+2x(y')^2=0$, satisfying the condition y(1) = 0, y'(1) = 1

(a) has no solution

(b) has a unique solution

(c) has two distinct solutions

(d) has an infinite number of solutions

The ordinary differential equation $x\frac{dy}{dx}-y=2x^2$ with initial conditions y(0) = 0 has (a) no solution

(b) a unique solution

(c) two distinct solutions

(d) an infinity of solutions

Consider the differential equation $y'=y^2-1$, x > 0 together with initial condition y(0) = $y_0$ Then for −1 < $y_0$ < 1, all the solutions y(x) are such that:

(a) y → −∞ as x → ∞.

(b) y → −1 as x → ∞.

(c) graph of y(x) is concave downwards.

(d) graph of y(x) is concave upwards.

Give five of your favourite metrics on $\mathbb{R^2}$.

Show that C[0, 1] is a metric space with metric $d_{\infty}(f,g):=||f-g||_{\infty}$. 

An open ball in a metric space (X, d) is given by

 $B_d(x,R):=\{ {y \in X:d(y,x)<R }\}$