α,β是方程X方-2X-1=0的两个不等实根
∴α²-2α-1=0 即α²=2α+1
且α+β=2,αβ=-1
α的四次方+12β
=（2α+1）²+12β
=4α²+4α+1+12β
=4（2α+1）+4α+1+12β
=12（α+β）+5
=24+5
=29