(x+1)(x+3)(x+5)(x+7)+15 =[(x+1)(x+7)][(x+3)(x+5)]+15 =(x^2+8x+7)(x^2+8x+15)+15 =(x^2+8x+7)[(x^2+8x+7)+8]+15 =(x^2+8x+7)^2+8(x^2+8x+7)+15 =[(x^2+8x+7)+3][(x^2+8x+7)+5] =(x^2+8x+10)(x^2+8x+12) =(x^2+8x+...