The coefficient of x7 in the expansion of (1 - x - x2 +x3)6 is :

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 Multiple Choice QuestionsShort Answer Type

171. The coefficients of the (r - 1)th, rth and (r + 1)th terms in the expansion of (x + 1)n are in the ratio 1 : 3 : 5. Find n and r. 
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 Multiple Choice QuestionsLong Answer Type

172.

Find the absolute term in the expansion of: open parentheses straight x minus 1 over straight x squared close parentheses to the power of 3 straight n end exponent

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173. The co-efficients of ar-1, ar and ar+1 in the expansion of (1 + a)n are in arithmetic progression, Show that n2 - n(4r + 1) + 4r2 - 2 =0. 
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 Multiple Choice QuestionsMultiple Choice Questions

174.

The sum of coefficients of integral powers of x in the binomial expansion of left parenthesis 1 minus 2 square root of straight x right parenthesis to the power of 50 space is

  • 1 half left parenthesis 3 to the power of 50 space plus space 1 right parenthesis
  • 1 half left parenthesis 30 to the power of 50 right parenthesis
  • 1 half left parenthesis 30 to the power of 50 minus 1 right parenthesis
  • 1 half left parenthesis 30 to the power of 50 minus 1 right parenthesis
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175.

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

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176.

A multiple choice examination has 5 questions. Each question has three alternative answers of which exactly one is correct. The probability that a student will get 4 or more correct answers just by guessing is

  • 17/35

  • 13/35

  • 11/35

  • 11/35

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177.

The term independent of  x in open parentheses fraction numerator straight x plus 1 over denominator straight x to the power of 2 divided by 3 end exponent minus straight x to the power of 1 divided by 3 end exponent space plus 1 end fraction minus fraction numerator straight x minus 1 over denominator straight x minus straight x to the power of 1 divided by 2 end exponent end fraction close parentheses to the power of 10 is 

  • 4

  • 120

  • 18

  • 18

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178.

If n is a positive integer, then open parentheses square root of 3 plus 1 close parentheses to the power of 2 straight n end exponent minus space left parenthesis square root of 3 minus 1 right parenthesis to the power of 2 straight n end exponent space is

  • an irrational number

  • an odd positive integer

  • an even positive integer

  • an even positive integer

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179.

The coefficient of x7 in the expansion of (1 - x - x2 +x3)6 is :

  • 144

  • -132

  • -144

  • -144


C.

-144

left parenthesis 1 minus straight x minus straight x squared plus straight x cubed right parenthesis to the power of 6
left parenthesis 1 minus straight x right parenthesis to the power of 6 left parenthesis 1 minus straight x squared right parenthesis to the power of 6
left parenthesis to the power of 6 straight C subscript 0 minus to the power of 6 straight C subscript 1 straight x to the power of 1 plus to the power of 6 straight C subscript 2 straight x squared minus to the power of 6 straight C subscript 3 straight x cubed plus to the power of 6 straight C subscript 4 straight x to the power of 4 minus space to the power of 6 straight C subscript 5 straight x to the power of 5 space plus to the power of 6 straight C subscript 6 straight x to the power of 6 right parenthesis
left parenthesis to the power of 6 straight C subscript 0 minus to the power of 6 straight C subscript 1 straight x squared space plus to the power of 6 straight C subscript 2 straight x to the power of 4 minus to the power of 6 straight C subscript 3 straight x squared space plus to the power of 6 straight C subscript 4 straight x to the power of 8 space plus...... plus to the power of 6 straight C subscript 6 straight x to the power of 12 right parenthesis
Now space coefficient space of space straight x to the power of 7 space equals space to the power of 6 straight C subscript 1 to the power of 6 straight C subscript 3 minus to the power of 6 straight C subscript 3 to the power of 6 straight C subscript 2 space plus to the power of 6 straight C subscript 5 to the power of 6 straight C subscript 1
space equals space 6 space straight x space 20 space minus space 20 space space straight x space 15 space plus 36
space equals space 120 minus 300 plus 36
space equals space 156 minus 300
space equals space minus 144 space space
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180.

The value of
(21C110C1) + (21C210C2) + (21C310C3) + (21C410C4) + .... +
(21C1010C10) is

  • 220 – 210

  • 221 – 211

  • 221 – 210

  • 221 – 210

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