great for verifying answers:
limit calculator – http://www.numberempire.com/limitcalculator.php
matrix calculator – http://www.bluebit.gr/matrix-calculator/
cramer’s rule calculator – http://sks99.com/ch9/deter/calcdeter.htm
another cramer’s rule calc – http://www.analyzemath.com/Calculators/Calculator_syst_eq.html
yet another cramer’s rule calc – http://ncalculators.com/matrix/cramers-rule-calculator.htm
partial fractions – http://calc101.com/webMathematica/partial-fractions.jsp
arithmetic sequence calculator – http://www.basic-mathematics.com/arithmetic-sequence-calculator.html
binomial theorem calculator – http://www.kusashi.com/binomial.php
tangent lines – http://cs.jsu.edu/~leathrum/Mathlets/tangents.html
taylor series expansion calc – http://www.solvemymath.com/online_math_calculator/calculus/taylor_series/index.php