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@ @QQU@ @pý†bɾa@ @
x +1 . 12
5
x
. 12 − 2
x
x + 1 12 − 2 = 12
5 x
12 − 2x + 12 − 2 = 12
5x 5
−2x + 12 − 2 = 0
5x 5
−10x 2 + 12 − 2x = 0
5x 2 + x − 6 = 0
(5x + 6)(x − 1) = 0
.x = 1 x >0 .x = −6 x = 1
5 ()
:( )
8 . 1600 .x
1600 + 10 .
x
x x −8
(x − 8) 1600 + 10 = 1600
x
(x − 8) 1600 + 10x = 1600
x
(x − 8)(1600 + 10x) = 1600x
1600x + 10x2 − 12800 − 80x = 1600x
10x2 − 80x − 12800 = 0
x 2 − 8x − 1280 = 0