Question

solve it step by step​

Answer 1

Answer:

The answer is

$343 {x}^{3} - 1323 {x}^{2} y + 1701x {y}^{2} - 729 {y}^{3}$

Explanation:

${(7x - 9y)}^{3} \\ = {(7x)}^{3} - 3 {(7x)}^{2}(9y) + 3(7x){(9y)}^{2} - {(9y)}^{3} \\ = 343 {x}^{3} - 27y(49 {x}^{2} ) + 21x(81 {y}^{2} ) - 729 {y}^{3} \\ = 343 {x}^{3} - 1323 {x}^{2} y + 1701x {y}^{2} - 729 {y}^{3}$