The coefficient of xn in expansion of (1+x)(1-x)n is from Mathe

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 Multiple Choice QuestionsMultiple Choice Questions

111.

If both the roots of the quadratic equation x2 – 2kx + k2 + k – 5 = 0 are less than 5, then k lies in the interval

  • (5, 6]

  • (6, ∞)

  • (-∞, 4)

  • (-∞, 4)

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112.

If the equation anxn +an-1xn-1 +....... +a1x =0, a1 ≠ 0, n≥2, has a positive root x =  α, then the equation nanxn-1 + (n-1)an-1xn-2 +......+a1 = 0 has a positive root, which is

  • greater than α

  • smaller than α

  • greater than or equal to α

  • greater than or equal to α

152 Views

113.

Let z, w be complex numbers such that z iw + = 0 and arg zw = π. Then arg z equals

  • π/4

  • 5π/4

  • 3π/4

  • 3π/4

956 Views

114.

If z = x – i y and z1/3 = p+ iq , then fraction numerator begin display style open parentheses straight x over straight p plus straight y over straight q close parentheses end style over denominator left parenthesis straight p squared plus straight q squared right parenthesis end fraction is equal to 

  • 1

  • -2

  • 2

  • 2

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115.

If (1 – p) is a root of quadratic equation x2 +px + (1-p)=0 , then its roots are

  • 0, 1

  • -1, 2

  • 0, -1

  • 0, -1

190 Views

116.

If one root of the equation x2+px+12 =0 is 4, while the equation x2 +px +q = 0 has equal roots, then the value of 'q' is

  • 49/3

  • 4

  • 3

  • 3

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117.

The coefficient of xn in expansion of (1+x)(1-x)n is

  • (n-1)

  • (-1)n(1-n)

  • (-1)n-1(n-1)2

  • (-1)n-1(n-1)2


B.

(-1)n(1-n)

The coefficient of xn in expansion of (1+x)(1-x)n is = coefficient of xn + coefficient of xn-1

left parenthesis negative 1 right parenthesis to the power of straight n space fraction numerator straight n factorial over denominator straight n factorial 0 factorial end fraction space minus fraction numerator straight n factorial over denominator 1 factorial left parenthesis straight n minus 1 right parenthesis factorial end fraction
space equals space left parenthesis negative 1 right parenthesis to the power of straight n space open square brackets fraction numerator straight n factorial over denominator straight n factorial 0 factorial end fraction minus fraction numerator straight n factorial over denominator 1 factorial left parenthesis straight n minus 1 right parenthesis factorial end fraction close square brackets
equals space minus space left parenthesis 1 right parenthesis to the power of straight n space left square bracket 1 minus straight n right square bracket

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118.

If 2a + 3b + 6c =0, then at least one root of the equation ax+ bx+ c = 0  lies in the interval

  • (0,1)

  • (1,2)

  • (2,3)

  • (2,3)

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119.

If x = ω – ω2 – 2. Then the value of (x4 + 3x3 + 2x2 – 11x – 6) is

  • 0

  • -1

  • 1

  • 1

186 Views

120.

If α, β ∈ C are the distinct roots, of the equation x2 -x + 1 = 0, then α101 + β107 is equal to

  • 2

  • -1

  • 0

  • 1


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