fullofquestions
Joined: 07 Oct 2007
Posts: 18
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| Posted: Fri Oct 26, 2007 2:04 pm Post subject: Algebra tricks / points to remember |
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Does anyone know of a list of pointers/"common blunders" for the algebra in the Math GRE? For now I have found the following link that has a basic list: http://tutorial.math.lamar.edu/pdf/Algebra_Cheat_Sheet.pdf
While studying for the test I've found many subtleties that lead to errors which are actual answers. Also, there are some tricks that really speed up the solution of a problem... For instance, below is a list of some of the mistakes I've made
v^w = e^(w log v) if w is not a constant
e^(2ln x) = e^(ln x^2) = x^2 NOT (e^(2ln x) = 2x)
e^(-ln x) = e^(ln x^-1) = x^-1 NOT (e^(-ln x) = -x)
b^(lob(base b) x) = x
log(cos x) = - log ((cos x)^-1)
infinity * 0 = 0 and such (I know that for many series questions when you are faced with an indeterminate form you have to use L'Hopital's rule).
the zero vector is not counted in the dimension of a vector space even though "every vector space must contain the zero vector"
etc |
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