Friday 21 June 2013

LOGARITHMS - 1



If Logy81 – log53125 = -1; find y

Solution

Logy81 – Log555 = -1        3135=5x5x5x5x5=55 by prime factorization

Logy81 – 5Log55 = -1

Logy81 – 5x1 = -1

Logy81 – 5 = -1

Logy81 = -1 + 5

Logy81 = 4

81 = y4                   81=3x3x3x3 = 34 by prime factorization

34 = y4

3 =y


Hence y = 3      





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