3A(8)M=4A(9)(M-1)
3[(8x7x......x(8-(m-1))]=4[(9x8x7x......x(9-(m-1-1))]
3x8x7x......x(8-m+1)=4x9x8x7x......x(9-(m-2))
3x8x7x......x(9-m)=4x9x8x7x......x(9-m+2)
3x8x7x......x(9-m)=4x9x8x7x......x(11-m)
8x7x......x(9-m)=4x3x8x7x......x(11-m)
8x7x......x(9-m)=12x8x7x......x(11-m)
8x7x......x(11-m)(10-m)(9-m)=12x8x7x......x(11-m)
(10-m)(9-m)=12
90-19m+m²敏闹=12
m²-19m+78=0
(m-6)(m-13)=0
m1=6
m2=13 不符合题桥耐罩意舍亩拦去。