If a,b,c are distinct numbers in arithmetic progression and roots of the quadratic equation (a+2b−3c)x2+(b+2c−3a)x+(c+2a−3b)=0 are α and β then both α and β belong to domain of
A
sin−1x
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B
sec−1(secx)
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C
sec(sec−1x)
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D
tan−1x
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Solution
The correct options are Asin−1x Bsec−1(secx) Dtan−1x Let A=a+2b−3c,B=b+2c−3a,C=c+2a−3b Since a,b,c are in AP b=a+d (d is common difference) c=a+2d αβ=c+2a−3ba+2b−3c=a+2d+2a−3a−3da+2a+2d−3a−6d=14 α+β=−(b+2c−3a)a+2b−3c=−(a+d+2a+4d−3a)a+2a+2d−3a−6d=54 α=14,β=1 ∴α,β=1,14
Domain of sin−1x is [−1,1]
Domain of sec−1(secx) is (0,π)−π2
Domain of sec(sec−1x) is R−(−1,1)
Domain of tan−1x is (−∞,∞) These values of α, β belong to the domain of A, B and D.