(x²-4x+2)(x²-4x+6)+4
=(x²-4x)²+8(x²-4x)+12+4
=(x²-4x)²+8(x²-4x)+16
=(x²-4x+4)²
=[(x-2)²]²
=(x-2)^4
∵a²+14a+49=25
∴a²+14a+24=0
(a+12)(a+2)=0
a+12=0或a+2=0
∴a=-12或a=-2
(x²-4x+2)(x²-4x+6)+4
=(x²-4x)²+8(x²-4x)+12+4
=(x²-4x)²+8(x²-4x)+16
=(x²-4x+4)²
=[(x-2)²]²
=(x-2)^4
∵a²+14a+49=25
∴a²+14a+24=0
(a+12)(a+2)=0
a+12=0或a+2=0
∴a=-12或a=-2