a) 7x+8y=9 wyznaczamy x 7x = 9 - 8y stąd x = (9 - 8y)/7 wstawiamy do drugiego 5x+6y=7 5(9 - 8y)/7 + 6y = 7 5(9 - 8y) + 42y = 49 45 - 40y + 42y = 49 2y = 49 - 45 2y = 4 y = 4/2 = 2 7x + 8y = 9 7x + 8 razy 2 = 9 7x + 16 = 9 7x = 9 - 16 = - 7 x = - 7/7 = - 1 x = - 1 , y = 2 sprawdzenie 7x + 8y = 9 7 razy - 1 + 8 razy 2 = 9 - 7 + 16 = 9 9 = 9 L = P 5x + 6y = 7 5 razy - 1 + 6 razy 2 = 7 - 5 + 12 = 7 7 = 7 L = P b) y+5x-7=0 wyznaczamy y = 7 - 5x i wstawiamy do drugiego x+2y=5 x + 2(7 - 5x) = 5 x + 14 - 10x = 5 - 9x = 5 - 14 - 9x = - 9 x = 9/9 = 1 x + 2y = 5 1 + 2y = 5 2y = 5 - 1 = 4 y = 4/2 = 2 x = 1 , y = 2 sprawdzenie y + 5x = 7 2 + 5 razy 1 = 7 2 + 5 = 7 7 = 7 L = P x + 2y = 5 1 + 2 razy 2 = 5 1 + 4 = 5 5 = 5 L = P
a) 7x+8y=9 /*5 5x+6y=7 /*7 35x+40y = 45 35x+42y = 49 35x = 45-40y 45-40y+42y = 49 2y = 4 /2 y=2 x=(-1) spr. 8*2+7(-1) = 16-7 = 9 6*2+5(-1) = 12-5 = 7 b) y+5x-7=0 x+2y=5 x = 5-2y y+5(5-2y) = 7 y+25-10y = 7 -9y = -18 /(-9) y = 2 x = 1 spr. 2+5*1 = 2+5 = 7 1+2*2 = 1+4 = 5
