Question

Using a suitable identity, determine the value of A) (17)^3+
(-12)^3+ (-5)^3and B) 64m^3 - 343n^3

Answer 1

17^3 + (-12)^3                        (x+y)^3= x^3+3x^2y+3xy^2+y^3

17^3 +3 x 17^2 x -12 + 3 x 17 x (-12)^2 + (-12)^3

4913 - 10404 + 7344 - 1728

12257 - 12132 = 125

64m^3 - 343n^3

(4m)^3 - (7n)^3                    x^3 - y^3= (x-y) (x^2 + xy + y^2)

(4m - 7n) { (4m)^2 + 4m x 7n + (7n)^2 }

(4m - 7n) (16m^2 + 28mn + 49n^2)

Hope it helps you ...