If a and b are the roots of the quadratic equation x2−4x+3=0, then (1+a+a2+a3...)(1+b+b2+b3+....) equal to
A
∞
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B
14
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C
−16
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D
none of these
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Solution
The correct option is A∞ x2−4x+3=0(x−1)(x−3)=0x=1or3∴a=3,b=1a+b=4,ab=31+a+a2+a3+........+∞=11−a(sumofinfiniteG.P.)∴(1+a+a2+a3+........+∞)(1+b+b2+b3+.......+∞)=(11−a)(11−b)=11−(a+b)+ab=11−4+3=10=∞