Question

sabendo que ab= 15, qual o valor de (a-b)*2-(a+b)*2

Answer 1

(a-b)^2-(a+b)^2=
(a-b)(a-b)-[(a+b)(a+b)]=
a^2-ab-ab+b^2-[a^2+ab+ab+b^2]=
a^2-2ab+b^2-[a^2+2ab+b^2]=
a^2-2ab+b^2-a^2-2ab-b^2=
-2ab-2ab=
-4ab=
-4.15=
-60