Given that - 3^1/3 + 3^-1/3 = x Prove that - 3x^3 - 9x - 10 = 0 Please help! PLEASE! My friend suggested something like taking 3^1/3 as 'a'.
Follow Math Help Forum on Facebook and Google+
Originally Posted by Ruler of Hell Given that - 3^1/3 + 3^-1/3 = x Prove that - 3x^3 - 9x - 10 = 0 Please help! PLEASE! My friend suggested something like taking 3^1/3 as 'a'. Cube the first equation: x^3 = 3 + 3*3^{2/3}*3^{-1/3} + 3*3^{1/3}*3^{-2/3} + 1/3 Now multiply through by 3: 3*x^3 = 10 + 9*[3^{1/3} + 3^{-1/3}] = 10 + 9*x rearrange and: 3x^3 - 9x - 10 = 0 RonL
View Tag Cloud