What is the value of the function y = 1/8x − 13 when x = −4 ?

To find the value of the function when x = -4, plug in x = -4 into the equation y = 1/8x - 13:

y = 1/8(-4) - 13
y = -1/2 - 13
y = -13.5

Therefore, the value of the function y = 1/8x - 13 when x = -4 is -13.5.