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Maths Puzzle
If a & b are the root of the equation 4x^2+3x+7=0, then 1/a+1/b=
a)-3/7
b)3/7
c)-3/5
d)3/5
e)-3/4
f)3/4
Read Solution (Total 4)
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- answer is a)-3/7
we know that a+b=-3/4 and ab=7/4
so 1/a+1/b=(a+b)/ab
=(-3/7) - 12 years agoHelpfull: Yes(2) No(0)
- replace x-->1/x
the equation become 4(1/x)^2+3(1/x)+7=0
==> 7x^2+3x+4=0 have two root 1/a & 1/b.
Sum of the roots= 1/a+1/b = -3/7 - 12 years agoHelpfull: Yes(2) No(1)
- 1/a+1/b =(a+b)/ab
by quad. eqn formula
=(-b/a)/(c/a)
=-3/4 * 4/7=-3/7 ans - 12 years agoHelpfull: Yes(2) No(0)
- ans:e
(1/a)+(1/b)=(a+b)/ab.....(1)
from given eqn
sum of root=a+b=-3/4
product of root=7/4
so,on putting the value in eqn(1)
ans will be -3/4
- 12 years agoHelpfull: Yes(0) No(1)
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