CBSE Class 10 Answered
polynomials
Asked by palaksophia | 05 Dec, 2009, 09:43: PM
Expert Answer
Let a,b and c are the zeroes of the polynomial f(x)=x^3-3px^2+qx-r.
Since it is given that they are in A.P
Therefore, a + c = 2b ................(1)
Sum of zeroes of a cubic polynomial, a + b + c = 3p .................(2)
Sum of zeroes taken two at a time, ab + bc + ca = q ..............(3)
Product of zeroes, abc = r .....................(4)
From (1) and (2), we get
3b = 3p ⇒ b = p ..........(5)
From (1) and (5), we get
ac = r/ p ..........(6)
Now from (2)
b (a + c) + ac = q
On substitution, we get
b (2b) + r/p = q
2p2 + (r/p) = q
2p3 + r = pq
2p3 = pq - r.
Hence option (a) is correct.
Answered by | 05 Jan, 2010, 10:22: AM
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