1.已知x y为实数y=根号x-2+根号2-x+3求3x+4y的值要使根号x-2+根号2-x有意义，有x-2≥0，2-x≥0即x≥2且x≤2，得x=2所以y=根号x-2+根号2-x+3=0+0+3=33x+4y=3X2+4X3=6+12=18
