Tuesday 25 February 2014

LOGARITHMS B36


If logx49 – log2128 = -5; find x

solution

logx49 – log2128 = -5

logx49 – log227 = -5

logx49 – 7log22 = -5

logx49 – 7 x 1 = -5

logx49 – 7 = -5

logx49 = -5 + 7

logx49 = 2

49 = x2

72 = x2      Powers cancel out

x = 7


Hence x = 7.

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