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Q.

If x is real, then the value of x2+34x-71x2+2x-7 does not lie between

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a

-9 and -5

b

-5 and 9

c

0 and 9

d

5 and 9

answer is D.

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Detailed Solution

Let y=x2+34x-71x2+2x-7

x2(y-1)+2(y-17)x+(71-7y)=0

For real values of x, its discriminant D0

4(y-17)2-4(y-1)(71-7y)0

(y2-3+y+289)-(71y-7y2-71+7y)0

y2-14y+450(y-5)(y-9)0

It is possible when both y-5 and y-9 are negative or both positive. Let y-50y5 and y-90y9.

Hence y5    ...(i)

If y-50y5 and y-90y9.

Hence y9.

Therefore y does not lie between 5 and 9.

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