f(x)=(x-5)(2x+7)(7x-3)f(x)=(x−5)(2x +7)(7x−3)f, left parenthesis, x, right parenthesis, equals, left parenthesis, x, minus, 5, right parenthesis, left parenthesis, 2, x, plus, 7, right parenthesis, left parenthesis, 7, x, minus, 3, right parenthesis has zeros at x=-3.5x=−3.5x, equals, minus, 3, point, 5, x=\dfrac{3}{7}x= 7 3 x, equals, start fraction, 3, divided by, 7, end fraction, and x=5x=5x, equals, 5. What is the sign of fff on the interval \dfrac{3}{7}