I'm having trouble solving these two problems:

1.)

2.)

Your assistance is much appreciated.

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- Mar 15th 2008, 11:51 AMcurrypuffTwo Logarithmic Function Problems
I'm having trouble solving these two problems:

1.)

2.)

Your assistance is much appreciated. - Mar 15th 2008, 12:00 PMwingless
Ignore the solution to the first question, there's a mistake in it.

log_c a + log_c b = log_c a.b

So,

log_2(x+7) + log_2(x) = 3

log_2{x^2 + 7} = 3

x^2 + 7 = 2^3 = 8

x^2 = 1

x={-1,1}

Don't forget to check the results because x+7 > 0 and x>0.

Ah, x = -1 doesn't satisfy x>0. So we remove it from the solution set.

x=1

----------------------------------------------

Let

Multiply both sides by a,

Put these a values back in ,

**(Not real!)**

(We exclude this because it's impossible to have such real x)

- Mar 15th 2008, 02:50 PMo_O
The rule should be:

Thus, a simple quadratic. - Mar 15th 2008, 02:56 PMwingless
Sorry, o_O is right. Ignore my solution to the first problem, I didn't multiply 7 by x. But the rest is similar, find the roots, check them for and .