a) x = 5, y = 1000
Ta có (x-5). (y+40) = (5-5) . (1000+40) = 0. 1040 = 0
b) .x=-10,y=15.
(x-5). (y+40) = (-10-5). ( 15+ 40) = -15 . 55 = -825
c) x = 16; y =-50
(x-5) . (y+40) = (16-5) . ( -50 + 40) = 11. (-10) = -110
d) 16.x = (-12).(-36) = 432
=> x = 432 : 16 = 27