Page 136 - aljaber

@ @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