$b)x^4+18^2$
$=x^4+324$
$=x^4+6x^3+18x^2-6x^3-36x^2-108x+18x^2+108x+324$
$=x^2.(x^2+6x+18)-6x.(x^2+6x+18)+18.(x^2+6x+18)$
$=(x^2-6x+18).(x^2+6x+18)$
$c)x^4+32^2$
$=x^4+1024$
$=x^4+8x^3+32x^2-8x^3-64x^2-256x+32x^2+256x+1024$
$=x^2.(x^2+8x+32)-8x.(x^2+8x+32)+32.(x^2+8x+32)$
$=(x^2-8x+32).(x^2+8x+32)$
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