Final answer:
To find the value of y when x = -8, given that y varies directly with x, we first find the constant of variation using the initial condition y=5 when x=4, which is k=5/4. Then, we calculate y as y=kx, which results in y = -10.
Step-by-step explanation:
Given that y varies directly with x and y = 5 when x = 4, we can find the constant of variation (k) by rearranging the equation of direct variation, which is y = kx. By substituting the given values, we have 5 = k(4), which implies k = 5/4. With the constant of variation known, we can then determine the value of y when x = -8. The equation would then be y = (5/4)(-8), resulting in y = -10.