which has roots , but as we are interested in real solutions for k we have does not give a real , so we are left with , then:
This is the way I thought of this problem too. Would have been nice if Greg used parentheses. Any way, your answer is off by a factor of 1/2. You went wrong during your substitution; answer should be: ln(3)/(2*ln(2)) or .7925. Obviously this is irrelevant since it's not even the question he's asking.