4: Use properties of rational and irrational numbers _Simplify square root expressions _Simplify expressions involving square roots by adding, subtracting, multiplying, and dividing _Rationalize the denominator of an expression containing a square root _Understand and explain why the sum or product of rational numbers is rational _Understand and explain why the sum of a rational number and an irrational number is irrational _Understand and explain why the product of a nonzero rational number and an irrational number is irrational