use intermediate value theorem to show f(x) has a zero
f(x)= x^5 - 4x^4- 7x^2 - 6x; [-0.7, -0.6]
f(-0.7)=-0.7^5-4(-0.7^4)-7(-0.7^2)-6(-0.7) = -.35847
f(-0.6)= substitue -0.6 in the equation = .48384
Assuming that f(x)= x^5 - 4x^4- 7x^2 - 6x = 0
Then solution would be
-.35847 < 0 < .48384