Question

Question #7b374

Answer 1

`x~~0.86887...`

Explanation:

There is not really an algebraic way to do this, besides Newton's method.

I used Symbolab (an online math engine like Wolfram-Alpha), and got `x~~0.86887...`.

An alternative way would be to graph `-6x^3-18x^2-4x+21=0`. graph{-6x^3-18x^2-4x+21 [-5.59, 4.41, -3.98, 1.02]}

If click on around `x=0.869`, it comes up with `y=0`, so `x=0.869` would also be a value.