Q). If n is a natural number, then 6 n – 5n always ends with
A) 7
B) 5
C) 3
D) 1
View Answer
D) 1
Explanation: f(n) = 6 n – 5n , n∈N
n = 1 ⇒ 6 – 5 = 1
n = 2⇒ 6 2 – 52 = 36 – 25 = 11
n = 3 ⇒ 6 3 – 53 = 216 – 125 = 91
always ends with’1′.
Q). If n(A) = 5, n(B) = 5 and n(A ∪ B) = 8, then n(A ∩ B) =
A) 2
B) 3
C) 1
D) None
View Answer
A) 2
Explanation: n(A ∪ B) = n(A)+n(B)-n(A ∩ B)
8 = 5 + 5- n(A ∩ B)
8 = 10 – n(A ∩ B)
∴ n(A ∩ B) =2
Q). If A = {x/x ∈ N, I < x < 10}, then n(A) =
A) 3
B) 4
C) 8
D) None
View Answer
C) 8
Explanation: A = { x/x ∈ N, I < x < 10}
∴ A = {2, 3, 4, 5, 6, 7, 8, 9}
∴n(A) = 8
Q). Identify the disjoint sets among the following:
A) A-B, B-A
B) A-B, A
C) B-A, B
D) None
View Answer
A) A-B, B-A
Explanation: A – B, B – A are disjoint sets.
Q). If two zeroes of the polynomial x3 + 3 x2 – 5x – 15 are √5 and – √5, then its third zero is
A) 3
B) 5
C) -3
D) -5
View Answer
C) -3
Explanation: Let α = √5 , β = √5
S1 = α+β + γ= -b/a
√5 – √5 + γ = -3/1
γ = -3
Q). If α and β are the zeroes of the polynomial f(x) = a x2 + bx +c, then 1/α + 1/β =
A) b/c
B) –b/c
C) c/b
D) –c/b
View Answer
B) –b/c
Explanation: α+β = -b/a , αβ = c/a
1/α + 1/β = α+β/αβ =
= -b/c
Q). If the diagram shows the graph of the polynomial f(x) = a x2 + bx + c, then
A) a > 0, b < 0 and c > 0
B) a < 0, b < 0 and c < 0
C) a < 0, b > 0 and c > 0
D) a < 0, b > 0 and c < 0
View Answer
A) a > 0, b < 0 and c > 0
Explanation: a > 0, b < 0 and c > 0
Q). If x = 2 + 22/3 + 21/3 , then the value of x3 – 6 x2 + 6x =
A) 3
B) 1
C) 2
D) -2
View Answer
C) 2
Explanation: x = 2 + 22/3 + 21/3
x-2 = 22/3 + 21/3
(x-2)2 = (22/3 + 22/3) 3. x3 – 8 – 6 x2 + 12 x
= = (22/3) 3 + (21/3) 3 + 3 . 22/3 . 21/3 (22/3 + 21/3 )
= 4 + -2 + 3(2) (x – 2)
∴ x3 – 8 – 6 x2 + 12 x = 6 + 6x – 12
∴ x3 – 6 x2 + 6 x = 2
Q). If am ≠bl, then the system of equations ax + by = c, lx + my = n
A) has a unique solution
B) has no solution
C) has infinitely many solutions
D) has two solutions
View Answer
A) has a unique solution
Explanation: a1 /a2 ≠b1 /b2
a/l ≠b/m
am ≠bl
has a unique solution
Q). The area of the triangle formed by the lines y = x, x = 6 and y = 0 is
A) 36 sq. units
B) 72 sq. units
C) 9 sq. units
D) 18 sq. units
View Answer
D) 18 sq. units
Explanation: y = x …. (1), x = 6………..(2) , y = 0…………..(3)
(1), (3) ⇒ A(0,0)
(1), (2) ⇒B(6, 6)
(2) ,(3) ⇒C(6,0)
Area =
=
=
=
= 36/2 = 18