Relation between Roots and Coefficients for Quadratic
lf the equati...
Question
lf the equations k(6x2+3)+rx+(2x2−1)=0 and 6k(2x2+1)+px+(4x2−2)=0 have both roots common, then the value pr is
A
12
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B
2
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C
1
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D
4
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Solution
The correct option is B2 Since the roots of the equations are common, the coefficients are in proportion. The first equation can be written as (6k+2)x2+rx+3k−1=0 The second one as(12k+4)x2+px+6k−2=0∴6k+212k+4=rp=3k−16k−2 ⇒3k+16k+2=3k−16k−2=3k+1+3k−16k+2+6k−2=12 ⇒Each ratio =12 ∴rp=12⇒pr=2