Question

(a-2)² - (a-1) (a+3)

Answer 1

$(a-2)^2-(a-1)(a+3)=\\(a^2-2*a*2+2^2)-(a*a+a*3-1*a-1*3)=\\(a^2-4a+4)-(a^2+3a-a-3)=\\a^2-4a+4-a^2-3a+a+3=7-6a$