Let S be the set of all real numbers. Then the relation R = {(a, b): 1 + ab > 0} on S is :

• reflexive and symmetric but not transitive

• reflexive and transitive but not symmetric

• symmetric and transitive but not reflexive

• reflexive, transitive and symmetric

Let $\mathrm{f}\left(\mathrm{x} + \frac{1}{\mathrm{x}}\right) = {\mathrm{x}}^2 + \frac{1}{{\mathrm{x}}^2}, \mathrm{x} \ne 0$, then f(x) equals to :

• x²

• x² - 1

• x² - 2

• x² + 1

Let f : R $\to$ R : f(x) = x² and g : R $\to$ R : g(x) = x + 5, then gof is :

• (x + 5)

• (x + 5²)

• (x² + 5²)

• (x² + 5)

The output s as a Boolean expression in the inputs x₁, x₂ and x₃ for the logic circuit in the following figure is

• x₁ x^'₂ + x^'₂ + x₃

• x₁ + x'₂x₃ + x₃

• (x₁x₂)' + x₁x'₂x₃

• x₁x'₂ + x'₂x₃

Let D₇₀ = {1, 2, 57, 10, 14, 35, 70} Define '+', '·' and '" by a + b = lcm (a, b), a . b = gcd (a, b) and a' = $\frac{70}{2}$ for all a, b $\in$ D₇₀. The value of (2 + 7)(14 . 10)' is

• 7

• 14

• 35

• 5

Let a be any element in a Boolean Algebra B. If a + x = 1 and ax = 0, then :

• x = 1

• x = 0

• x = a

• x = a'

then s is equal to :

• x . (y' + z)

• x . (y' + z')

• x . (y + z)

• (x + y) . z

248.

If N_a = {an : n $\in$ N}, then N₅ n N₇ is equal to :

• N₇

• N

• N₃₅

• N₅

If $\mathrm{f}\left(\mathrm{x}\right) = \frac{\mathrm{\alpha x}}{\mathrm{x} + 1}, \mathrm{x} \ne - 1$, for what value of $\mathrm{\alpha }$ is f$\left[\mathrm{f}\left(\mathrm{x}\right)\right]$ = x ?

• $\sqrt{2}$

• $- \sqrt{2}$

• 1

• - 1

Let D = {1, 2, 35, 6, 10, 15, 30}. Define the operattons '+', ' . ' and ' ' ' on D as follows a + b = LCM(a, b), a . b = GCD(a, b) and a' = $\frac{30}{\mathrm{a}}$ Then (15' + 6) · 10 1s equal to :

• 1

• 2

• 3

• 5