✨ Best Answer ✨
参考・概略です
(x+1)(x+3)(x+5)(x+7)+15
={(x+1)(x+7)}{(x+3)(x+5)}+15
={x²+8x+7}{x²+8x+15}+15
={(x²+8x)+7}{(x²+8x)+15}+15
=(x²+8x)²+22(x²+8x)+105+15
=(x²+8x)²+22(x²+8x)+120
={(x²+8x)+10}{(x²+8x)+12}
={x²+8x+10}{x²+8x+12}
={x²+8x+10}{(x+2)(x+6)}
=(x+2)(x+6)(x²+8x+10)
遅くなってすいません!!ありがとうございます!