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**SHEvA9** thank you a lot

I agree with what you said

and i got case 2 as it is the same thing as case 1

the two factors are negative, the inequality will be reversed when you multiply by negative denominator then reverse it back after dividing by negative sign of the nominator, right?

one last thing, " 3,000 Solved Problems in Calculus " is a book i am trying to finish so that i could be ready to study Math in Canadian university, is it a good book? i mean not just in terms of the language i also want to improve my math skills, is the book useful for this purpose? **Sorry, but I don't know this book. Remember I live in Germany. Look into the Member's list who's living in Canada and ask her/him by PM.**