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Square Roots and Real Numbers
If , then x is a square root of y . A
rational number, like 81, whose square root, 9, is a rational
number, is called a perfect square . The number 81 has two square
roots, 9 and - 9. The radical sign is used to indicate a nonnegative or principal
square root. For example, A square root of a positive rational number that is
not a perfect square is an irrational number. An irrational
number is a number that cannot be expressed in the form , where a and b are integers and b 0. The set of rational numbers and the set of
irrational numbers together form the set of real numbers . The
graph of the set of all real numbers is the entire number line.
, then x is a square root of y . A
rational number, like 81, whose square root, 9, is a rational
number, is called a perfect square . The number 81 has two square
roots, 9 and - 9. The radical sign 
is used to indicate a nonnegative or principal
square root. For example, 
A square root of a positive rational number that is
not a perfect square is an irrational number. An irrational
number is a number that cannot be expressed in the form 
, where a and b are integers and b 
0. The set of rational numbers and the set of
irrational numbers together form the set of real numbers . The
graph of the set of all real numbers is the entire number line.