Question

If x-y=12 and xy=27 ,find the value of
x³-y³

Answer 1

(x-y)^3=x^3-y^3-3xy(x-y)
12^3=x^3-y^3-3×27×12
1728-972=x^3-y^3
x^3-y^3=756

Answer 2

${x}^{3} - {y}^{3} = {(x - y)}^{3} + 3xy( x - y) \\ {x}^{3} - {y}^{3} = {(12)}^{3} + 3 \times 27(12) \\ {x}^{3} - {y}^{3} =2700$