Please help, basic algebra. Find the value of x

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

Evaluate the discriminant of each equation. tell how many solutions each equation has and whether the solutions are real or imaginary. x^2 - 4x - 5 = 0

Select the correct answer. what is the exact value of sin (157.5°)? a. 'sqrt(2 - sqrt(2))/2 b. *"-"'sqrt(2 + sqrt(2))/29 c.'sqrt(2 + sqrt(2))/4" d. "-"sqrt(2 + sqrt(2))/4)