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Maths Puzzle
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For what value of âkâ will the equation (2kx2 + 5kx +2)=0 have equal roots?
A. 2/7 B. 9/4 C. 16/25 D. 7/1
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Read Solution (Total 2)
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- D=b^2-4ac
for real and equal roots D=0
here a= 2k b=5k c=2
D=(5k)^2-(4*2k*2)=0
k=16/25 - 6 years agoHelpfull: Yes(3) No(1)
- C. 16/25
Quadratic equation 2kx^2+5kx+2=0 is of the form ax^2+bx+c=0 so here a=2k, b=5k, c=2
If r1 & r2 are the roots of the equation and r1=r2, then Sum of the roots=r1+r2=2r1=-b/a=-5k/2k=-5/2 ---(i) and
Product of the roots=r1*r2=r1^2=c/a=2/(2k) =1/k---(ii)
From (i), r1=-5/4, substituting this value in (ii), (-5/4)^2=1/k, So k=16/25
- 8 years agoHelpfull: Yes(0) No(7)
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