有關中五的數學一問

1) 4x+y-2= x^2 ....(1)x+y-20=0 ....(2)By (2) , y = 20 - x , sub it to (1) :4x + (20 - x) - 2 = x^2x^2 - 3x - 18 = 0(x - 6)(x + 3) = 0x = 6 , y = 20-6 = 14
or
x = - 3 , y = 20+3 = 23
2)x^2 + y^2 = x - y + 2 = 4x^2 + y^2 = 4 ....(1)
x - y + 2 = 4 ....(2)By (2) :y = x - 2 , sub it to (1) :x^2 + (x - 2)^2 = 42x^2 - 4x + 4 = 4x^2 - 2x = 0x(x - 2) = 0x = 0 , y = 0 - 2 = - 2orx = 2 , y = 2 - 2 = 0