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Solve: log2(x) + log2(x + 2) = 3

2007-06-29 16:10:47 · 2 answers · asked by Anonymous in Science & Mathematics Mathematics

2 answers

log2(x) + log2(x + 2) = 3
log2[x^2 + 2x] = log2 8
x^2 + 2x - 8 = 0
(x-2)(x+4) = 0
x = 2 or x = -4
x= -4 rejected because x must be > 0 for logarithms to be defined.

2007-06-29 16:13:54 · answer #1 · answered by Anonymous · 0 0

log[2] x + log[2] (x+3) = 3
log[2] x(x+3) = 3
x(x+3) = 2^3 = 8
x² + 3x - 8 = 0
x = -3/2 ± [√(9 + 32)]/2
x = -3/2 ± (√41)/2
can't use neg solution since log neg is undefined, so
x = -1.5 + 3.2016
x = 1.70156

2007-06-29 23:17:15 · answer #2 · answered by Philo 7 · 0 1

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