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.y = x :( ) ()
3 ()
. f (y) = (3y)2 + 3y + 1 = 9y2 + 3y + 1
f (3z) = 81z2 + 9z + 1 = 7
81z 2 + 9z + 1 = 7
81z2 + 9z − 6 = 0
27z2 + 3z − 2 = 0
(9z − 2)(3z + 1) = 0
.z2 = 2 z1 = −1
9 3
. z1 + z2 = −1 + 2 = −1
3 9 9
x :( )
.y
2x + 6y = 224
4x + 3y = 250
−2
−6x = −276 :( ) ()
. x = −276 = 46 y
−6
x
.
