In order to find the value of f(-2), you can plug -2 wherever x is.
f(x) = 6x^2 - 4
f(-2) = 6(-2)^2 - 4
f(-2) = 6(4) - 4
f(-2) = 24 - 4
f(-2) = 20
Thus, the value of f(-2) is 20. Hope this helps! If you have any other questions related to this, let me know.