Find the value(s) of x for which the expression is undefined: 6x−1x2+4x−5
+4 or+1
-5 or +1
-5 or -1
+5 or -1
16
Correct answer is B
6x−1x2+4x−5
The expression is undefined when x2+4x−5=0
x2+5x−x−5=0
x(x+5)−1(x+5)=0
(x−1)(x+5)=0
The expression is undefined when x = 1 or -5.
If R = [2, 4, 6, 7] and S = [1, 2, 4, 8], then R∪S equal
[1,2,4,6,7,8]
[1,2,4,7,8]
[1,4.7,8]
[2.6.7]
[2.4]
Correct answer is A
R = {2, 4, 6, 7}; S = {1, 2, 4, 8}
R ∪ S = {1, 2, 4, 6, 7, 8}
lf 16/9 , x, 1, y are in Geometric Progression (GP), find the product of x and y.
9/16
3/4
1
4/3
16/6
Correct answer is C
16/9, x, 1, y => a, ar, ar2, ar3
ar2 = 1 => 16r2/9 = 1 => 16r2
9 => r2 = 9/16 => r = 3/4
ar2 = y = ar2 x r = 1 x 3/4 = 3/4
x xy = 4/3 x 3/4 = 1
Find the nth term Un of the A.P., 11, 4, -3,....... .
Un=19+7n
Un=19-7n
Un=18+7n
Un= 18-7n
Un= 17-7n
Correct answer is D
A.P 11, 4, -3
1st term = 11
A.P = a, a + d, a + 2d ...... a + (n - 1)d
If a = 11
a + d = 4
d = 4 - 11 = -7
nth term = a + (n-1)d
= 11 + (n-1)(-7)
= 11 - 7n + 7
= 18 - 7n