Question

10a+(a+5)(a-5)+(a-5)^2

Answer 1

$10a + {a}^{2} - 25 + {a}^{2} - 10a + 25 = \\ 2 {a}^{2}$

Answer 2

10а+(а+5)(а-5)+(а-5)^2=10а+а^2-5а-5а+25+(а-5)^2=а^2+25+(а-5)^2=a^2+25-а^2-25=а^2-а^2+25-25=0