Also, since you are saying that your textbook lacks the guide that Khan Academy gives, you can always, ALWAYS use the internet. There is always a reward for extra precautions, so yes, I would say use both.

It has pros and cons from both sides that seem to be in one but not the other which is why it is thoroughly important for you to cover both guides because this way IF you miss anything that seems major or even minor that might be important for test prep by chance, it won't exactly escape from your clutches as you would be reviewing the topic from both sides and who knows, you might even get a super-strong grip on the subject due to the fact that you reviewed it from both sides and understood it. The reason why I am suggesting this is that since you are saying, according to what I understand, is that Khan Academy has a more understandable guide but maybe not exactly a very deepness while your textbook has more deepness in it but not the guide.

Use the textbook and the Khan Academy platform. My suggestion would be that you use both.

Khan academy pre calc