The zeroes of the function are the values of x which make it equal to zero
Since f(x) = (2x + 6)(x - 4)
Then to find the zeroes of f, equate f(x) by 0

Equate each bracket by 0 to find x

Subtract 6 from each side

Divide both sides by 2


Add 4 to each side

The zeroes of the function are x = -3 and x = 4
The answer is C