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chapter 10 Identities, the above identity is called the identity of the…
chapter 10 Identities
10.1 Meaning of identities
we learn algebraic expressions
and equations in book 1A
example
x+3 is an algebraic expression
x+3=5 is an equation
A. tests for identities
we need to check L.H.S. and R.H.S.
is or isn't the same to present
it is or is not an identities
B. finding unknown constants
in an identity
for any identity, the L.H.S. and the R.H.S
are exactly the same after simplification
We can use this property to find the unknows
constants in an identity
example
Ax +Bx+C三2x -4x+3
by comparing the like terms,
A=2,B=-4,C=3.
10.2 difference of two squares
we need to use a formula to calculate
the difference square
(a+b)(a-b)三a -b
10.3 perfect square
in this section we will talk about
perfect square (a+b) and (a-b)
(a+b) =a +2ab+b
(a-b)=a -2ab+b
we also can use this to
calculate some different squares
example
401 x 401
solution:
401 x 401 = (400+1) x (400+1)
=160000+800+1
=16801
the above identity is called the
identity of the
difference of two square