Essentially, differentials allow us to solve the problems presented in the previous examples from a slightly different point of view. Recall, when {{MATH_320}} is near but not equal zero, {{MATH_321}} Hence, {{MATH_322}} We can replace a quantity {{MATH_323}} with a quantity {{MATH_324}} to write {{ENV_325}} Adding {{MATH_326}} to both sides we see {{MATH_327}} or, equivalently {{MATH_328}} There are contexts where the language of differentials is common. Here is the basic strategy: {{CMD_329}} {{ENV_330}} {{CMD_331}}