def p(x):
    return x**3 - 3*x**2 - 2*x + 1


def es_decreixent(a, b, delta):
    trobat = False
    xprev = a
    x = xprev + delta
    px = p(xprev)
    while x <= b:
        pxprev, px = px, p(x)
        trobat = pxprev <= px
        if trobat:
            break
        xprev, x = x, x + delta
    if trobat:
        r = False, x
    else:
        r = True, 0.0
    return r