Решение:
1) $$(m-5)^2 = m^2 - 2*5*m + 5^2 = m^2 - 10m + 25$$
2) $$(2a + 7b)^2 = (2a)^2 + 2*2a*7b + (7b)^2 = 4a^2 + 28ab + 49b^2$$
3) $$(a + 3)(a - 3) = a^2 - 3^2 = a^2 - 9$$
4) $$(8x + 5y)(5y - 8x) = (5y + 8x)(5y - 8x) = (5y)^2 - (8x)^2 = 25y^2 - 64x^2$$
Ответ:
1) **$$m^2 - 10m + 25$$**
2) **$$4a^2 + 28ab + 49b^2$$**
3) **$$a^2 - 9$$**
4) **$$25y^2 - 64x^2$$**