I don't quite understand the definition of sufficient condition and necessary condition. I've seen the definition many times, but I still can't understand it. Tell me about the following two questions· 1. For any real number a, B, C, the true proposition is (b) A. "Ab > BC" is the necessary condition of "a > b", and "AC = BC" is the necessary condition of "a = B" C. "AC > BC" is a sufficient condition for "a > b" and "AC = BC" is a sufficient condition for "a = B" 2. It is known that a and B are real numbers which are not equal to 0. What is the condition for "A / b > 1" to be "a > b"? And prove your conclusion

I don't quite understand the definition of sufficient condition and necessary condition. I've seen the definition many times, but I still can't understand it. Tell me about the following two questions· 1. For any real number a, B, C, the true proposition is (b) A. "Ab > BC" is the necessary condition of "a > b", and "AC = BC" is the necessary condition of "a = B" C. "AC > BC" is a sufficient condition for "a > b" and "AC = BC" is a sufficient condition for "a = B" 2. It is known that a and B are real numbers which are not equal to 0. What is the condition for "A / b > 1" to be "a > b"? And prove your conclusion

From condition a, we can deduce that condition B holds ~ then a is the sufficient condition of B ~ B is the necessary condition of a ~ 1 options a and C: these two options belong to the same type. For unequal sign, when both sides multiply / divide by negative number, they will change sign, so "ab > BC" and "a > b" can't deduce each other, so it's wrong; for equal sign, a