(a-3)/a
(-x^2-9x)/(x^2-9)
x is not equal -1 and 2, the area is 50/3
(a-bc)/(a-1)
(x+3)/(x-3)
1
Condition of existence: x is not equal 5, the person's speed is: 30(km/h)
(2x^2-x+3)/(x+1)(x-2)
x is not equal 1,-1,3,-3
mọi x thuộc tập R