To revise about the ninth class first of all you should be clear with your 8
after revising the 8 concepts
take the textbook or any reference from you seniors and just go lesson by lesson so that you will have a continuty
if you have any doubt you can ask in brainly
According to me, Revise all ur class 8th concepts thoroughly so that u know them well.
If u know someone in class 10th ask them to gve their old class 9th textbooks for a few days... u can read from those textbooks so that u know which concepts will happen in the next class