<span>а). -0,7*9,31+0,69*(0,7)=0,7*(0,69-9,31)=-6,034.
б). (-5/8+7/9)*7,2=7,2*(-5*9+7*8)/72=1,1.
в) 14*(2 1/14-5/7)=14*(29/14-5/7)=14*((29-2*5)/14)=19.</span>
(x-y)×(x+y)=4
-4x-4y=4
x+y=-1
y+x=4
x=2
3/4-1/2=1/4
-4×1/4=-1
×-7/15=-1
×=-1-7/15
×=-1 целая 7/15
1) 2(х-2у)=х-8у
2х-4у=х-8у
2х-х=-8у+4у
х=-4у
х=-4
2) 5(х+у)=2(х-у)+10
5х+5у=2х-2у+10
5х-2х=-2у+10-5у
3х=-7+10
х=-7/3у+10/3