1) (2a - 5)^2 = (2a - 5)(2a - 5) = 4a^2 - 10a - 10a + 25 = 4a^2 - 20a + 25
2) (x + 3y) = x + 3y
3) (7 - x)(7 + x) = 49 - 7x + 7x - x^2 = 49 - x^2
4) x^3 - 9x
1) (2a - 5)^2 = (2a - 5)(2a - 5) = 4a^2 - 10a - 10a + 25 = 4a^2 - 20a + 25
2) (x + 3y) = x + 3y
3) (7 - x)(7 + x) = 49 - 7x + 7x - x^2 = 49 - x^2
4) x^3 - 9x