Упростить(m-3)*(m-7)-(m-5)^2

Question

Упростить
(m-3)*(m-7)-(m-5)^2

Answer 1

(m-3)(m-7)-(m-5)^2= m^2-7m-3m+21-(m^2-10m+25)= m^2-7m-3m+21-m^2+10m-25=-7m-3m+21+10m-25=-10m+10m+21-25=21-25=-4
Ответ: -4