I can't figure out this one please help!!

Which value is not a solution of 8x^3 – 1 = 0

Asmall business produces and sells balls. the fixed costs are $20 and each ball costs $4.32 to produce. each ball sells for $8.32. write the equations for the total cost, c, and the revenue, r, then use the graphing method to determine how many balls must be sold to break even.

Find the percent error of the measurement 4 cm