21. If the equations x 2 + ax + b = 0 and x 2 + cx + d = 0 have a common root and the firstequation have equal roots, then prove that 2(b + d) = ac
maheshchary , 9 Years ago
Grade 12th Pass
1 Answers
rajnish kumar
Last Activity: 9 Years ago
let root of first be p,p. and root of second be p,q. now. p= -a/2. p^2=b.. and pq=d p+q=-c. now... take lhs... 2( p^2+ pq). 2(p(p+q)).that is 2(p(-c)). and also p=-a/2... therefore lhs get ac. hence prooved
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