Question 20379
a little mental leap is required here.


Let {{{y=x^2}}}, so that {{{y^2 = x^4}}}. Are these definitions OK?


Right, {{{x^4 - 3x^2 - 4}}} then becomes {{{y^2 - 3y - 4}}} which is a normal quadratic that factorises easily to (y-4)(y+1). 


Hence, we have {{{(x^2 - 4)(x^2 + 1)}}}


jon.