Question

y=分子是x平方-2x-1 分母是x平方-5x+6 求值域

Answer 1

(x^2-5x+6)y=x^2-2x-1

(y-1)x^2+(2-5y)x+6y+1=0

(2-5y)^2-4(y-1)(6y+10>=0

y^2+8>=0

y为一切实数