= 80 + 0,9 *(-1000) = 80 -900 = - 820
6/7*(-0,79)-2,74*6/7=6/7( -0,79-2,74)=6/7*(-3,53)=6/7*(-3 53/100)=6/7*(-353/100)=
= -1059/350= -3 9/350
\\\\\\\\\\\\\\\\\\\\\\\\\\\\\\
(х+4у)/у=10
х+4у=10*у
х=10у-4у =6у
(7х-у)/х =(7*6у -у)/6у= (42у-у)/6у =41/6
3(x+1)(x-1)=2(x-2)(x+2)+x²+2x
3х²-3=2х²-2+х²+2х
2х=-2+3
2х=1
х=1:2
х=0,5
Ответ: 0,5