Решите уравнения:  а) 7(2 + у) - 3у = 5у - 6 б) 4х - 2(3 + х) = 9 - х г) -3(5а - 1) +4а = 2а + 7(5 - 3а) 

a) 7(2+y)-3y=5y-6; 14+7y-3y=5y-6; 14+4y=5y-6; 4y-5y=-6-14; -y=-20; y=20!   б) 4x-2(3+x)=9-x; 4x-6-2x=9-x; 2x-6=9-x; 2x+x=9+6; 3x=15; x=5!   г) -3(5a-1)+4a=2a+7(5-3a); -15a+3+4a=2a+35-21a; -11a+3=-19a+35; -11a+19a=35-3; 8a=32; a=32/8; a=4!  

а) [latex]7(2+y)-3y=5y-6[/latex]   [latex]14+7y-3y=5y-6[/latex]   [latex]14+4y=5y-6[/latex]   [latex]5y-4y=14+6[/latex]   [latex]y=20[/latex] _______________________________________________________ [latex]7(2+20)-3\cdot20=5\cdot20-6[/latex] (это проверка)   [latex]7\cdot22-60=100-6[/latex]   [latex]154-60=94[/latex]   [latex]94=94[/latex] ======================================================== б) [latex]4x-2(3+x)=9-x[/latex]   [latex]4x-6-2x=9-x[/latex]   [latex]2x-6=9-x[/latex]   [latex]2x+x=9+6[/latex]   [latex]3x=15[/latex]   [latex]x=15:3[/latex]   [latex]x=5[/latex] __________________________________________ [latex]4\cdot5-2(3+5)=9-5[/latex]   [latex]20-2\cdot8=4[/latex]   [latex]20-16=4[/latex]   [latex]4=4[/latex] ============================================================== г) [latex]-3(5a-1)+4a=2a+7(5-3a)[/latex]   [latex]-15a+3+4a=2a+35-21a[/latex]   [latex]-11a+3=35-19a[/latex]   [latex]19a-11a=35-3[/latex]   [latex]8a=32[/latex]   [latex]8a=32[/latex]   [latex]a=32:8[/latex]   [latex]a=4[/latex] ___________________________________________________ [latex]-3(5\cdot4-1)+4\cdot4=2\cdot4+7(5-3\cdot4)[/latex]   [latex]-3(20-1)+16=8+7(5-12)[/latex]   [latex]-3\cdot19+16=8+7\cdot(-7)[/latex]   [latex]-57+16=8-49[/latex]   [latex]-41=-41[/latex]