Tom K. answered 03/28/21
Knowledgeable and Friendly Math and Statistics Tutor
Note that the problem does not say rational zeroes. I may have entered wrongly, but I saw a solution near 1.949158859 and only one real solution - from the alternating nature of the signs, we know all solutions will be positive; the odd power guarantees at least one solution; the relatively small linear and cubic coefficients guide us toward there being only one solution. Note the plot from 0 to 2