If the coefficients of x3 and x4 in the expansion of (1+ax+bx2)(

Subject

Mathematics

Class

JEE Class 12

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 Multiple Choice QuestionsMultiple Choice Questions

1.

If X = {4n - 3n-1 : n ε N} and Y = {9(n-1):n εN}; where N is the set of natural numbers,then X U Y is equal to

  • N

  • Y-X

  • X

  • X

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2.

If z is a complex number such that |z|≥2, then the minimum value of open vertical bar straight z space plus space 1 half close vertical bar

  • is equal to 5/2

  • lies in the interval (1,2)

  • is strictly greater than 5/2

  • is strictly greater than 5/2

287 Views

3.

If a ε R and the equation - 3(x-[x]2 + 2(x-[x] +a2 = 0(where,[x] denotes the greatest integer ≤ x) has no  integral solution, then all possible value of  lie in the interval

  • (-1,0) ∪ (0,1)

  • (1,2)

  • (-2,-1)

  • (-∞,-2) ∪ (2, ∞)

182 Views

4.

Let α and β be the roots of equation px2 +qx r =0 p ≠0. If p,q and r are in AP and 1 over straight alpha space plus space 1 over straight beta = 4, then the value of |α- β| is

  • fraction numerator square root of 61 over denominator 9 end fraction
  • fraction numerator 2 square root of 17 over denominator 9 end fraction
  • fraction numerator square root of 34 over denominator 9 end fraction
  • fraction numerator square root of 34 over denominator 9 end fraction
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5.

If the coefficients of x3 and x4 in the expansion of (1+ax+bx2)(1-2x)18 in powers of x are both zero, then (a,b) is equal to

  • open parentheses 16 comma 251 over 3 close parentheses
  • open parentheses 14 comma 251 over 3 close parentheses
  • open parentheses 14 comma 272 over 3 close parentheses
  • open parentheses 14 comma 272 over 3 close parentheses


D.

open parentheses 14 comma 272 over 3 close parentheses

In expansion of (1+ax+bx2)(1-2x)18,
Coefficient of x3 = Coefficient of x3 in (1-2x)18
+Coefficient of x2 in a(1-2x)18
+Coefficient of x in b(1-2x)18
 = - negative straight C presuperscript 18 subscript 3.2 cubed space plus space straight a straight C presuperscript 18 subscript 2.2 squared minus straight b to the power of 18 straight C subscript 1.2 space equals space 0
rightwards double arrow fraction numerator 18 space straight x 17 space straight x space 16 over denominator 3 space straight x 2 end fraction.8 space plus space straight a. fraction numerator 18 space straight x 17 over denominator 2 end fraction 2 squared minus straight b.18.2 space equals 0
rightwards double arrow space 17 straight a minus straight b space equals space fraction numerator 34 space straight x space 16 over denominator 3 end fraction space space... space left parenthesis straight i right parenthesis
Similarly space coefficient space of space straight x to the power of 4
straight C presuperscript 18 subscript 4.2 to the power of 4 space plus space straight a straight C presuperscript 18 subscript 3.2 cubed minus straight b to the power of 18 straight C subscript 2.2 squared space equals space 0
therefore space 32 straight a minus 3 straight b equals space 240
On space solving space Eqs. space left parenthesis straight i right parenthesis space and space left parenthesis ii right parenthesis space we space get
straight a space equals space 16 space straight b space equals space 272 over 3

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6.

The angle between the lines whose direction cosines satisfy the equations l +m+n=0 and l2 = m2+n2 is

  • π/3

  • π/4

  • π/6

  • π/6

199 Views

7.

Three positive numbers form an increasing GP. If the middle term in this GP is doubled, then new numbers are in AP. Then, the common ratio of the GP is

  • square root of 2 plus square root of 3
  • 3 plus square root of 2
  • 2 minus square root of 3
  • 2 minus square root of 3
250 Views

8. limit as straight x space rightwards arrow 0 of space fraction numerator sin begin display style left parenthesis end style begin display style straight pi end style begin display style space end style begin display style begin display style cos end style squared end style begin display style straight x end style begin display style right parenthesis end style over denominator straight x squared end fraction space is space equal space to
  • π/2

  • 1

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9.

If (10)9 +2 (11)2(10)7 + .....+10 (11)9 = K(10)9, then k is equal to

  • 121/10

  • 441/100

  • 100

  • 100

192 Views

10.

If PS is the median of the triangle with vertices P(2,1), Q(6,-1) and R (7,3), then equation of the line passing through (1,-1) and parallel to PS is

  • 4x-7y - 11 =0

  • 2x+9y+7=0

  • 4x+7y+3 = 0

  • 4x+7y+3 = 0

182 Views

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