Page 50 - Math Course 2 (Book 1)

Introduction to Real Numbers

Rational approximation
MO. 2 - L1c
A rational approximation of an irrational number is a
rational number that is close to, but not equal to, the
Square Roots of Real Numbers value of the irrational number.

a rational approximation of 2 is 1.41
Vocabulary A-Z

Let us learn some vocabulary
Let’s Begin

Square root
Find Square Roots
is one of two equal factors of a number.

As 64, is 8 since 8 x 8 or 8 is 64. Example
2

16
Find –
Perfect square 9

A number like 64, with a square root that is a rational Represents the negative square
number, is called a perfect square. – 16 root of 16
9 9
A number such as 3 is the square root of a
number that is not a perfect square. It cannot
16
4
2
be expressed as a terminating or repeating 16 = ---> = – 4
–
decimal. 3 = 1.73205080. 9 3 9 3
16 4
Answer – = –
Radical sign 9 3

A square root is indicated by the symbol , which
is called a radical sign. REAL WORLD EXAMPLE

radical sign SPORTS SCIENCE
or symbol. 86321 radicand Find the surface area of an athlete whose
height is 147 centimeters and whose weight
is 48 kilograms.

Principal square root height • weight Write the formula.
3600
the non-negative square root of the number under
the radical sign. = 147 • 48 Replace height with 147 and
3600 weight with 48.
64 = 8 64 indicates the principal square Simplify.
root of 64. = 7056
3600

– 64 = –8 – 64 indicates the negative
square root of 64. = 1.96 or 1.4 m² Simplify.

+ 64 indicates both square roots
+ 64 = + 8 of 64. The surface area of the athlete is
Answer
1.4 m .
2
42