Sun The sun is the center of the solar system, it is a star, a hot ball of glowing gases. Supply To furnish organs, tissues or cells with a vital element as blood or never fibers. Support To keep going, to uphold. Surroundings The circumstances, conditions or objects by which one is surrounded.
1. Solving Differential Equations (DEs). A differential equation (or DE) contains derivatives or differentials. Our task is to solve the differential equation. This will involve integration at some point, and we'll (mostly) end up with an expression along the lines of  y = ....
Example: Solve the differential equation: dy/dx = y + 1, y(0) = 1 The general solution is: y = c*e^x - 1 for any real constant c. The particular solution you are interested in is the one where y(0) = 1, that is, c*e^0 - 1 = 1, that is, c = 2, that is: y = 2*e^x - 1 - Doctor Rob, The Math Forum http://mathforum.org/dr.math/