M的二次方+2M+1-N的平方
=(m+1)²-n²
=(m+1+n)(m+1-n)
=(m+n+1)(m-n+1)
.
X的4次方-X的3次方+X的2次方+2X-1
=x的4次幂-1 -(x³+1) +x²+2x+1
=(x+1)(x-1)(x²+1)-(x+1)(x²-x+1)+(x+1)²
=(x+1)[(x-1)(x²+1) - (x²-x+1)+(x+1)]
=(x+1)(x³-x²+x-1-x²+x-1+x+1)
=(x+1)(x³-2x²+3x-1)