Step-by-step explanation:
x and y trade places.
y = 2x² - 4
y + 4 = 2x²
x² = (y + 4)/2
x = ±sqrt((y + 4)/2)
and for the usual notation we rename x to y and vice versa
y = ±sqrt((x + 4)/2)
and this is not a function, because there are now 2 result values for every input value.
