求下列函数的定义域:(1)y=根号x²-4x+9(2)y=根号-2x²+12x-18

问题描述:

求下列函数的定义域:
(1)y=根号x²-4x+9
(2)y=根号-2x²+12x-18

(1)∵y=根号x²-4x+9
∴x²-4x+9≥0(这没有实数解)△<0
(2)∵y=根号-2x²+12x-18
∴-2x²+12x-18 ≥0
(-2X+6)*(X-3)≥0
(2X-6)*(X-3)≤0
∴X=3