Saturday, November 17, 2012

log 2 (x+5) + log 2 (x+2) = log 2 (x+6)

 log 2 (x+5) + log 2 (x+2) = log 2
(x+6)


We know that log x + log y = log
x*y


==> log 2 (x+5)(x+2) = log 2
(x+6)


We know that if log x = log y ==>
x=y


==> (x+5)(x+2) =
(x+6)


Open
brackets:


==> x^2 + 7x + 10 =
x+6


==> X^2 + 6X + 4
=0


==> x =[ -6 +
sqrt(36-16)]/2


           = [-6 + sqrt(20)] /
2


           = [-6 +
2sqrt(5)]/2


            = -3 +
sqrt(5)


==> the answer is x = -3 +
sqrt(5)

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