Solve x^4+2x^2-3=0
The trick with this question is noticing the hidden quadratic as quartic equations are unsolvable at A-level.
Letting u=x^2 the question becomes u^2+2u-3=0 which most students would be able to solve.
To factorise this then we must find two numbers that add to 2 and multiply to give -3, i.e. 3 and -1.
Therefore factorising this becomes: (x+3)(x-1)=0 x therefore equals -3 and 1
BS
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