Question

почему 3^15-3^12 = 3^12(3^3 - 1)?

Answer 1

$3^{15}-3^{12}=3^{12}*3^3-3^{12}=3^{12}(3^3-1)$

можно и так

$3^{15}-3^{12}=3^{12}(3^{15-12}-1)=3^{12}(3^3-1)$