Question

Объясните, пожалуйста.

Answer 1

$a(-15 ; - 8)\\ \beta a(-15 \beta ;-8 \beta )\\\\| \beta a|= \sqrt{(-15 \beta ) ^{2} +(-8 \beta ) ^{2} }= \sqrt{225 \beta ^{2}+64 \beta ^{2} }= \sqrt{289 \beta ^{2} } =17 \beta \\\\17 \beta =34\\\\ \beta =2$