In a test, I have a question to simplify logarithms. In a quetions, the correct answer is lg(a-b). If the student writes this, this will be correctly interpreted as the base-10 logarithm of a-b, but the answer will be evaulated as incorrect, stating that the correct answer is lg(a-b,10). This error occured only recently, the past few years this has not been an issue.
Can someone tell me what is wrong?
Thanks in advance,