How many real roots does the equation x2 + 3|x| + 2 = 0 

Subject

Mathematics

Class

NDA Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

A binary number is represented by (cdccddcccddd)2, where c > d What is its decimal equivalent ?

  • 1848

  • 2048

  • 2842

  • 2872


2.

Let S = {2, 4, 6, 8, ..........20}. What is the maximum number of subsets does S have ?

  • 10

  • 20

  • 512

  • 1024


3.

Consider the following statements in respect of the quadratic equation 4(x p)(x q) r2 = 0, where p, q and r are real numbers:

1) The roots are real

2) The roots are equal if p = q and r = 0

Where of the above statements is/are correct ?

  • 1 only

  • 2 only

  • Both 1 and 2

  • Neither 1 nor 2


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4.

How many real roots does the equation x2 + 3|x| + 2 = 0 have ?

  • 1 only

  • 2 Only

  • Both 1 and 2

  • Neither 1 nor 2


A.

1 only

The given equation is: x2 + 3x + 2 = 0

We can open the mode as 

x2 + 3x + 2 = 0 for x > 0x2 - 3x + 2 = 0 for x < 0

When you calculate the roots of the equations 

x2 + 3x + 2 = 0 for x > 0 roots are -2, -1 (which is not possible as x > 0 )

x2 - 3x + 2 = 0 for x < 0 roots are 2, 1 (which is also not possible as x < 0)

Hence, option A is correct.


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5.

If xlog7x > 7 where x > 0, then which one of the following is correct ?

  • x  0, 

  • x  17, 7

  • x  0, 17  7, 

  • x  17, 


6.

What is the solution of x ≤ 4, y ≥ 0 and x ≤ 4, y ≤ 0 ?

  • x ≥ 4, y ≤ 0

  • x ≤ 4, y ≥ 0

  • x ≤ 4, y = 0

  • x ≥ 4, y = 0


7.

If 3rd, 8th and 13th terms of a GP are p, q and r respectively, then which one of the following is correct ?

  • q2 = pr

  • r2 = pq

  • pqr = 1

  • 2q = p + r


8.

Let Sn be the sum of the first n terms of an AP. If S2n = 3n + 14n2, then what is the common difference ?

  • 5

  • 6

  • 7

  • 9


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9.

How many two-digit numbers are divisible by 4 ?

  • 21

  • 22

  • 24

  • 25


10.

Let a, b, c be in AP and k ≠ 0 be a real number. Which of the following are correct ?

1) ka, kb, kc are in AP

2) k –a, k -b, k –c are in AP

3) ak, bk, ck are in AP are in AP

Select the correct answer using the code given below :

  • 1 and 2 only

  • 2 and 3 only

  • 1 and 3 only

  • 1, 2 and 3 


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