from typing import Tuple


def extend_bounds(
    min_x: float, min_y: float, max_x: float, max_y: float, extend_amount: float
) -> Tuple[float, float, float, float]:
    """
    Extend bounds by addition and reduction.

    >>> extend_bounds(0, 0, 10, 10, 10)
    (-10, -10, 20, 20)
    """
    return (
        min_x - extend_amount,
        min_y - extend_amount,
        max_x + extend_amount,
        max_y + extend_amount,
    )