1.∫ The arithmetic square root is positive.

∴ 3x-4=5

x=3

2. The arithmetic square root of ∵ 9 is a, and the absolute value of b is 4.

∴a=3,b= 4

∴a-b=3-4=- 1

Or a-b=3-(-4)=7.

3. The arithmetic square root of ∵ 2a-1is 3, and the arithmetic square root of 3a+b- 1 is 4.

∴2a- 1=9,a=5

3a+b- 1= 16，b = 17-3a = 17- 15 = 2

4.√√( x-4)≥0，√(4-x)≥0

∴x-4≥0,x≥4

4-x≥0，x≤0

∴x=4

∴y=√(x-4)+√(4-x)+4=4

∴√x+√y=√4+√4

=2+2=4