Because limits have the unique ability to determine values at discontinuities, it is much more efficient to evaluate with limits than regular substitution. https://en.wikibooks.org/wiki/Calculus/Proofs_of_Some_Basic_Limit_Rules Before using limit properties, you must show that both limits and exist

Identity Rule

Constant Rule

if and for any constants then

Sums & Difference Rule

The limit of the sum, is the sum of the limits.

Scalar Product Rule

Product Rule

Quotient Rule

Power Rule

Limit of the power is the power of the limit