If α,β∈R are the roots of the equation (a2+b2)x2+2x(ac+bd)+c2+d2=0, then αβ is equal to
A
1
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B
2
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C
12
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D
14
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Solution
The correct option is A1 (a2+b2)x2+2(ac+bd)x+c2+d2=0 Roots are real. ⇒Δ≥0 ⇒4(ac+bd)2−4(a2+b2)(c2+d2)≥0 ⇒(ac+bd)2−[(ac)2+(bd)2+(bc)2+(ad)2]≥0 ⇒2acbd−(bc)2−(ad)2≥0 ⇒−(bc−ad)2≥0 ⇒(bc−ad)2≤0 ⇒(bc−ad)2=0 ⇒bc=ad So, the roots are real and equal.