Question

а2+10а+25+(5-а)(а-5) при а=-2.8
срочно даю 30 баллов​

Answer 1

Ответ:

$a=-2,8\ \ ,\ \ \ a^2+10a+25+(5-a)(a-5)=\underbrace{(a^2+10a+25)}_{(a+5)^2}-\underbrace{(a-5)(a-5)}_{(a-5)^2}=\\\\=(a+5)^2-(a-5)^2=\Big((a+5)-(a-5)\Big)\Big((a+5)+(a-5)\Big)=\\\\\\=10\cdot 2a=20a=20\cdot (-2,8)=-56$