At the beginning of a drawing class, the instructor suggests that an illusion of depth may be created in a two-dimensional picture by including parallel lines that converge at a vanishing point. Your instructor is making reference to a monocular depth cue known as:

Your instructor is making reference to a monocular depth cue known as: Linear perspective.  

Step-by-step explanation:

Your instructor is making reference to a monocular depth cue known as: Linear perspective.  

We know that is: Linear perspective, a system of creating an illusion of depth on a flat surface. All parallel lines in a painting or drawing using this system converge in a single vanishing point on the composition’s horizon line.

x =±sqrt(1/3)

step-by-step explanation:

x+4/6x=1/x

multiply each side by 6x to get rid of the fractions

6x*(x+4/6x)=1/x*6x

distribute

6x^2 +4 = 6

subtract 4 from each side

6x^2 +4-4 = 6-4

6x^2 =2

divide by 6

6x^2/6 = 2/6

x^2 = 1/3

take the square root of each side

sqrt(x^2) = ±sqrt(1/3)

x =±sqrt(1/3)