[(0.87) 3 + (0.13) 3] / [(0.87) 2 - 0.87 x 0.13 + (0.13) 2] =?

Given Expression = ( a³ + b³ )/ (a² + b² - ab) where = 0.87 and b = 0.13
= [(a + b ) (a² + b² - ab)] / (a² + b² - ab)
= a + b
= 0.87 + 0.13
= 1