Решите все 4 системы методом подстановки a) x+7y=-6 2x-5y=7 б)2x-5y=9 x+4y=-2 в) x-2y=-7 4x+5y=11 г) 3x+2y=2 1/2x-3y=-1/2

х + 7у = - 6    → х = -6 - 7у2х - 5у = 7    → 2(- 6 - 7у) - 5у= 7  → - 12 - 14у - 5у = 7  → - 19у = 19 →  у = - 1х + 7у = - 6  → х + 7*(-1) = - 6  → х = 7 - 6  → х = 1х = 1 ;  у = - 1---------------------------------------------------------------------------------2х - 5у = 9х + 4у = - 2 → х = - 2 - 4у2(- 2 - 4у) - 5у = 9 → - 4 - 4у - 5у = 9 → - 9у = 9 + 4 → у = -13/9 → у = - 1целая 4/92х  - 5*- 1 49 = 9; → 2х = 9 - 65/9; → 2х = 9 - 7 2/9; → 2х = 1целая7/9; → х = 8х = 8у = - 1 4/9----------------------------------------------------------------------------------------х - 2у = - 7; → х = 2у - 74х + 5у = 11; → 4(2у - 7) + 5у = 11; → 8у - 28 + 5у = 11;→ 13у = 39; → у = 3х - 2у = - 7; → х - 2*3 = - 7; → х = 6 - 7; → х = - 1х = - 1у = 3---------------------------------------------------------------------------------------3х + 2у = 2; 0,5х - 3у = - 0,5; → 0,5х = ( - 0,5 + 3у); → х = ((0,5 (-1 + 6)) / 0,5; → х = -1+ 6; → х = 53х + 2у = 2; → 3*5 + 2у = 2; → 2у = 2 - 15; → 2у = - 13; → у = - 6,5х = 5у = - 6,5

a) x=-6-7y2*(-6-7y)-5y=7-12-14y-5y=7-19y=19y=-1x=-6-7*(-1)=-6+7=1b) x=-2-4y2*(-2-4y)-5y=9-4-8y-5y=9-12y=12y=-1x=-2-4*(-1)=-2+4=2c) x=2y-74*(2y-7)+5y=118y-28+5y=1113y=39y=3x=2*3-7=-1d) x=(2-2y)/3=2/3*(1-y)1/2*2/3*(1-y)-3y=-1/21/3-1/3y-3y=-1/2-10/3y=-1/2-1/3=-5/6y=-5/6/(-10/3)=5/6*3/10=1/4x=2/3*(1-1/4)=2/3*3/4=1/2