Which inequality represents all the values of x for which the quotient below is defined?
√8x^2 / √2x

a x > = 0
b x> 1
c x> 0
d x> -1

For "less than or equal to" you can use <= 
For "greater than or equal to" you can use >= 

√(15(x−1)) / √(2x^2) 

Value under square root must be ≥ 0 
Value in denominator not = 0 

15(x−1) ≥ 0 
x−1 ≥ 0 
x ≥ 1 

2x^2 > 0 
x^2 > 0 
x ≠ 0 

Combining both inequalities, we get: 

x ≥ 1

Just divide the x axis (the top) by 2 or multiply the y axis (the bottom) by 2