Step-by-step explanation:

1} (4A - 3)³ - (4a + 3)³

using (x - y)³ = x³ - y³ - 3XY(x - y)

= (4a)³ - (3)³ - 3 × 4a × 3(4a - 3) - (4a + 3)³

= 64a³ - 27 - 36a(4a - 3) - (4a + 3)³

= 64a³ - 27 - 144a² + 108a - (4a + 3)³

= 64a³ - 144a² + 108a - 27 - (4a + 3)³

using (x + y)³ = x³ + y³ + 3xy(x + y)

= 64a³ - 144a² + 108a - 27 - (4a)³ + (3)³ + 3 ×

4a × 3(4a + 3)

= 64a³ - 144a² + 108a - 27 - 64a³ + 27 + 36a(4a +

3)

= 64a³ - 144a² + 108a - 27 - 64a³ + 27 + 144a² +

108a

= 64a³ - 144a² + 108a - 27 - 64a³ + 144a² + 108a +

27

= 64a³ - 64a³ - 144a² + 114a² + 108a + 108a + 27 -

27

= 216a

2} (5x - 7y)³ + (5x + 7y)³

= using (x - y)³ = x³ - y³- 3xy(x - y)

= (5x)³ - (7y)³ - 3 × 5x × 7y(5x - 7y) + (5x + 7y)³

= 125x³ - 343y³ - 105xy(5x - 7y) + (5x + 7y)³

= 125x³ - 343y³ - 525x²y - 735xy² + (5x + 7y)³

= 125x³ - 525x²y + 735xy² - 343y³ + (5x + 7y)³

using (x + y)³ = x³ + y³ + 3xy(x + y)

= 125x³ - 525x²y + 735xy² - 343y³ + (5x)³ + (7y)³ +

3 × 5x × 7y(5x + 7y)

= 125x³ - 525x²y + 735xy² - 343y³ + 125x³ + 343y³

+ 105xy(5x + 7y)

= 125x³ - 525x²y + 735xy² - 343y³ + 125x³ + 343y³

+ 525x²y + 735xy²

= 125x³ - 525x²y + 735xy² - 343y³ + 125x³ +

525x²y + 735xy² + 343y³

= 250x³ + 1470y²