Q.
The equation xx+12+xx−12=a(a−1) has
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a
four real roots if a > 2
b
four real roots if a < - 1
c
two real roots if 1 < a < 2
d
no real root if a < - 1
answer is A.
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Detailed Solution
xx+12+xx−12=a(a−1) or xx+1+xx−12−2xx+1xx−1=a(a−1) or 2x2x2−12−2x2x2−1−a(a−1)=0 or t2−t−a(a−1)=0 where t=2x2x2−1⇒ t=a or 1−a⇒ 2x2x2−1=a or 2x2x2−1=1−a⇒ x=±aa−2 or x=±a−1a+1When a<−1⇒all roots are real12⇒all roots are real
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