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@ @QRS@ @pý†bɾa@ @
( ) 5x − 5y = 100
( ) 9x − 12y = 0
5 () −9 ( )
( ) −45x + 45y = −900
( ) 45x − 60y = 0
() ()
−15y = −900
. y = −900 = 60 ()
−15
:( )
x −1− x +1+1 = 0
x −1 = x +1−1
(x − 1) = (x + 1) − 2 x + 1 + 1
x − 1 − x − 1 − 1 = −2 x + 1
−3 = −2 x + 1
9 = 4(x + 1)
9 = 4x + 4
. 4x = 9 − 4 = 5
:( ) ( )
.r + s = 3 rs = 1
r 2 + s2 = r 2 + 2rs + s2 − 2rs = (r + s)2 − 2rs = 32 − 2(1)
=7