a) 2x - 3y = 7 / * 5 3x - 5y = 11 / * (-3) 10x - 15y = 35 -9x + 15y = -33 x=2 x =2 10*2 - 15y =35 x=2 -15y=35-20 x=2 -15y=15 / : (-15) x=2 y= -1 b) 5p - 2r = 21 / * 5 3p + 5r = -6 / * 2 25p -10r = 105 6p +10r = -12 31p = 93 /: 31 p = 3 p=3 6*3 +10r = -12 p=3 10r= -12 - 18 p=3 10r= -30 / : 10 p=3 r= -3 c) 2x - 3y = 10 / * 5 5x + 5y = 0 / * 3 10x - 15y= 50 15x + 15y= 0 25x=50 / :25 x=2 x=2 5*2+5y=0 x=2 5y= - 10 / :5 x=2 y= -2
a {2x-3y=7 -> 2x=3y-7 -> x=1,5y-3,5 3x-5y=11 3(1,5y-3,5)-5y=11 4,5y - 10,5 -5y =11 -0,5y=21,5 y=-43 x= 61 b) 5p - 2r = 21 / * 5 3p + 5r = -6 / * 2 25p-10r=105 6p+10r=-12 31p=93 p=3 75-10r=105 10r=30 r=3 c {2x-5y=10 ->5y=10-2x 5x+5y=0 5x +10-2x=0 3x=-10 x=-10/3 5y=10+6 2/3 5y=50/3 y=10/3 d {5v1+4v2=4 7v1+5v2=6 e {4x+5y=12,3/x3 3x-2y=-4/x -4 12x+15y=36,9 -12x+8y=16 23y=52,9 y=2,3 x=0,2 f {3x-0,2y=35 -> y=15x-175 2,5x-5y=5 2,5x-75x+875=5 -72,5x=-870 x=12 y=5
