Let heads means 1 and Tails means 2 while tossing a coin. The coefficients of a quadratic equation ax 2 +bx+c=0 are chosen by tossing 3 fair coins.The chance that the roots of quadratic equation are non-real is? a)3/8 b)7/8 c)5/36 d)11/36

Chilukuri Sai Kartik Grade: 12

        Let heads means 1 and Tails means 2 while tossing a coin.

The coefficients of a quadratic equation ax²+bx+c=0 are chosen by tossing 3 fair coins.The chance that the roots of quadratic equation are non-real is?

a)3/8

b)7/8

c)5/36

d)11/36

8 years ago

Answers : (1)

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Mir Noaman Ali IIT-Roorkee

57 Points

							a can be filled in 2 ways(head=1 and tails=2) similarly b in 2 ways and c also in 2 ways so total number of ways = 8 let the probability that the roots are real is x and non real becomes 1-x let us calulate x first, x means it must have real roots  discriminant greater that or equal to zero b*2 >= 4ac of those 8 equally probable cases there is only 1 case( when b=2, a=c=1   when coin corresponding to a and c gets a head and coin corresponding to b gets a tail which satisfies this case so probability =1/8 hence x=1/8 so required answer is 1-x = 7/8       ....................... please approve my answer if you have understood the solution

8 years ago

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