[tex]\text{If (-3, y) lies on the graph of}\ \ y = \left(\dfrac{1}{2}\right)^x, \text{then substitute x = -3}\\\text{ to the equation and calculate y}:\\\\y=\left(\dfrac{1}{2}\right)^{-3}=(2)^3=8\\\\Answer:\ \boxed{y=8}\\\\Used:\ a^{-n}=\dfrac{1}{a^n}[/tex]
