a) 2x-2y=7/2 x-y=3,5 x=3,5+y 4x+3y=21 x=3,5+y 4(3,5 + y) +3y=21 x=3,5+y 14 + 4y + 3y = 21 7y=7/7 y=1 x=4,5
a) 2x-2y=7 4x+3y=21 2x = 7+2y 4x +3y =21 x = (7+2y):2 4(7+2y):2 + 3y =21 x = (7+2y):2 2(7+2y) +3y =21 x = (7+2y):2 14 +4y +3y = 21 x = (7+2y):2 7y = 21-14 x = (7+2y):2 y = 7:7 x = (7+2*1):2 y = 1 x = 4,5 y = 1 b) 0,4x+0,3y=1,4 /*10 0,1x+3y=2,3 /*10 4x +3y = 14 x + 30y = 23 x + 30y = 23 4x +3y = 14 x = 23-30y 4( 23- 30y ) + 3y = 14 x = 23-30y 92 -120y +3y =14 x = 23-30y -117y =14-92 x = 23-30y -117y = -78 x = 23-30y y = 78/117 x = 23-30*(2/3) y = 2/3 x = 23-20 = 3 y = 2/3 x = 3 y = 2/3 c) 0,5x-2y=8 /*2 2x+5y=6 x -4y = 16 2x +5y = 6 x = 16+4y 2(16+4y) +5y =6 x = 16+4y 32 + 8y +5y = 6 x = 16+4y 13y = 6 -32 x = 16+4y y = -26 :13 x = 16+4*(-2) y = -2 x = 16 -8 =8 y = -2 x = 8 y = -2
